OBJECTIVES: Physiological and psychophysical studies have provided evidence that the sensory information must be integrated with past experience through the process of perception. This study was performed to investigate whether mnemonic information acquired about dentistry effects the process of oral sensory perception. METHODS: When we mechanically stimulated one of the lower teeth of students belonging to the school of Dental Hygiene at Kyushu Dental College, they answered which tooth had been stimulated. All lower teeth except for the third molar were randomly stimulated. Some subjects have also participated in the same experiment in the past years. The students in upper and lower grade at school were defined as the subjects who have large and small information acquired about dentistry, respectively. RESULTS: In most of the subjects, the ratio of correct answers for the anterior teeth was significantly higher than that for the posterior teeth. The ratio of correct answers and the variance of incorrect answers significantly correlated to the respondent^,s year in school. On the other hand, there was no correlation between the ratio of correct answers and the results of term examinations at school that must be involved in the semantic memory about dentistry. CONCLUSION: These findings suggest that mnemonic information acquired about dentistry, but not semantic memory, seems to be involved in the process of oral sensory perception. [J Physiol Sci. 2007;57 Suppl:S102]

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To elucidate the role of TRPA1, a member of the TRP family of mediating membrane depolarization by opening cation channels, on noxious transmission in the spinal dorsal horn, we investigated the effects of TRPA1 agonists cinnamaldehyde (CA) and allyl isothiocynate (AI) on synaptic transmission in substantia gelatinosa (SG) neurons of adult spinal dorsal horn. Whole-cell patch-clamp recordings were performed from SG neurons of spinal cord slice preparations. Under current-clamp conditions, CA increased the frequency of excitatory postsynaptic potentials (EPSPs) in SG neurons tested, some of which elicited a burst of action potentials. Under voltage-clamp conditions, CA dose-dependently (300 μM- 1 mM) increased the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) while it increased only the frequency of miniature EPSCs (mEPSCs) observed in presence of 1 μM of TTX. At higher doses, CA gave a desensitizing effect. On the other hand, they had no effects on the frequency and amplitude of both glycinergic and GABAergic mIPSCs. The effects of CA and AI on mEPSCs were blocked by application of a TRP antagonist ruthenium red (30 μM). These findings suggest that TRPA1 receptors are expressed at the presynaptic terminals but not postsynaptic membranes in the SG and their activation by CA or AI enhances the excitatory but not glycinergic and GABAergic synaptic transmission. Such presynaptic activation of TRPA1 receptors may increase the gain of cold noxious transmission. [J Physiol Sci. 2007;57 Suppl:S102]

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To elucidate how primary afferents responding to specific sensory modalities are sorted and connected with their target dorsal horn (DH) neurons, synaptic responses evoked in DH neurons were compared between wild and cadherin-8 (cad8, a cell-cell adhesion molecule) knockout mice. Cad8 was expressed by restricted populations of superficial DH neurons and small-diameter neurons in dorsal root ganglion, the majority of which co-expressed TRPM8. The amplitude of EPSCs evoked in superficial DH neurons by the activation of slow-conducting fibers in cad8 -/- mice was significantly smaller than that in wild mice. In cad8-expressing DH neurons, CNQX-sensitive fast and slow miniature EPSCs were elicited in the same cells. Menthol selectively increased the frequency of the slow mEPSCs. However, this effect was not observed in cad8 -/- mice. On the other hand, no differences were found in the amplitude of [Ca²⁺]i in small DRG neurons in response to menthol and in the facilitation of miniature release by capsaicin between wild and cad8-/- mice. The present results suggest that menthol-sensitive (TRPM8-expressing) afferent fibers transmit cool sensation to superficial DH neurons through Cad8-expressing synapses and Cad8 has an essential role in determining of the synaptic connectivity. [J Physiol Sci. 2007;57 Suppl:S102]

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It is known that there exist two different response components of the CT nerve for sweeteners in mice, one is inhibited by gurmarin [gurmarin-sensitive (GS)] and the other is not [gurmarin-insensitive (GI)]. The C57BL strain possesses both components in the taste buds innervated by the CT nerve, whereas BALB mice almost exclusively have the GI component. Recently, it has been found that TRPM5 is a highly temperature-sensitive, heat-activated channel, and increasing temperature between 15 and 35°C markedly enhances the CT nerve responses to sweeteners in wild-type but not in TRPM5 knockout mice. In the current study, therefore, we examined the temperature dependency of GS and GI sweet taste responses of the CT nerve in C57BL/6N and BALB/c mice. In both mice, the CT nerve responses to all sweeteners before and after lingual treatment with gurmarin increased significantly on increasing the temperature from 15 to 35°C. Comparing the GS and GI components, we found that increase of response of the GS component was smaller than that of the GI component at the higher temperature range (increasing temperature from 25 to 35°C). In addition, responses to non-caloric sweeteners were larger in the GS than the GI component, whereas the reverse was true for sugars responses. These results suggest that 1) both GS and GI components exhibit the temperature sensitivity, and 2) the temperature sensitivity of sweet responses differs between GS and GI components, and 3) response of GS and GI components differs among sweet compounds. [J Physiol Sci. 2007;57 Suppl:S102]

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Amiloride, a epithelial Na⁺ channel bloker, is known to inhibit responses to NaCl of taste cells and the chorda tympani (CT) nerve innervating the anterior tongue in various mammalian species. In mice, amiloride sensitivity varies among strains; C57BL/6 (B6) mice exhibited inhibition of NaCl responses by amiloride to -50% of control, whereas NaCl responses were only slightly inhibited by amiloride (-20% of control) in 129P3/J (129) mice. The amiloride-sensitive epithelial Na⁺ channel (ENaC) expressed in taste cells is a potent candidate to play a role in the salt responses. In this study, using amiloride-sensitive B6, amiloride-weakly sensitive 129 strains and their F2 hybrids, we investigated possible relationships of the amiloride sensitivity with single nucleotide polymorphisms (SNPs) of three subunits of ENaC (α, β, γ) in the anterior tongue. The results showed that sequencing detected a SNP resulted in an amino acid substitution, R616W in αsubunit. No SNP was found in β and γsubunits. F2 hybrid mice were divided into 3 groups according to their αENaC R616W genotypes (129/129, B6/129 and B6/B6). Responses of the CT nerve to 0.03-0.3 M NaCl decreased after amiloride treatment in B6 and F2 (B6/129 and B6/B6), whereas only weak inhibition was evident in 129 and F2 (129/129). These results suggest that R616W of ENaC αsubunit may be one of factors responsible for mouse strain differences in amiloride sensitive salt responses. [J Physiol Sci. 2007;57 Suppl:S103]

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Gurmarin (Gur), a polypeptide isolated from the plant Gymnema sylvestre, is known to selectively inhibit responses of the chorda tympani (CT) nerve to sweet compounds in rodents. In mice, the sweet-suppressing effect of Gur differs among strains. Responses to sweet compounds in the chorda tympani (CT) nerve were inhibited to < 50% of control by Gur in C57BL/6 but only slightly if at all in BALB/c (BALB) mice. These two mouse strains possess different alleles of the sweet receptor gene, Sac (Tas1r3) (taster genotype for C57BL/6 and non-taster genotype for BALB/c mice). This raises the possibility that polymorphisms of Tas1r3 may account for differential sensitivity to Gur.To investigate this possibility, we examined the effect of Gur on CT responses to sweet compounds in another Tas1r3 non-taster strain, 129X1/Sv mice. Our results indicated that this non-taster strain exhibited significant inhibition by Gur of CT responses to various sweet compounds similar to that observed in C57BL mice having the Tas1r3 taster genotype. This suggests that the mouse strain difference in the Gur inhibition of sweet responses of the CT nerve may not be associated with polymorphisms of Tas1r3. [J Physiol Sci. 2007;57 Suppl:S103]

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Umami taste, the taste of amino acids such as L-glutamate, is a pleasant gustatory sensation for the detection of protein and amino acids contents in foods. A number of G-protein coupled receptors have been proposed as umami receptor, including T1r1/T1r3 hetero dimmer, taste mGluR4 and taste mGluR1. In addition, transduction of umami has been shown to involve many intracellular signaling components. In the mouse chorda tympani nerve, there are at least 4 types of fibers responding to glutamate, suggesting multiple reception and transduction mechanisms for umami taste. In this study, we examined umami taste response of mouse fungiform taste cells. The apical restricted stimulation of monosodium glutamate (MSG) induced an increase in firing frequency in some taste cells. These cells were primarily divided into 2 groups. One responded best to sweeteners (S-group) and the other responded best to MSG (M-group). Taste cells in both groups were further classified into 2 groups according to the synergism between MSG and inosin-5'-monophosphate (IMP). One showed the robust synergism (S1 and M1) and the other did not (S2 and M2). These results were consistent with those of mouse chorda tympani nerve fibers, suggesting existence of multiple reception and transduction mechanisms for umami taste and selective signal transmission from taste cells to gustatory nerve fibers. Supported by JSPS Grants-in-Aid 18077004, 18109013 (YN) and 17791325 (RY). [J Physiol Sci. 2007;57 Suppl:S103]

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Recent molecular studies proposed that various receptors, such as taste mGluR4, heterodimers of T1R1/T1R3, taste mGluR1, and brain-type mGluR4, might underlie umami taste. To date, however, the roles in umami taste of each of these receptors and their downstream signaling molecules have not been made clear. Apparently contradictory data was obtained from two T1R3 knock-out (KO) mouse models: Zhao et al. (2003) showed that umami detection and perception was abolished in their T1R3 KO, while we found that responses to umami compounds were diminished in our T1R3 KO mice. In the present study, we further examined responses to umami compounds at single nerve fiber levels in wild type (WT), T1R3-KO and TRPM5-KO mice. The results indicated that umami-responsive single fibers of the chorda tympani nerve in WT mice could be classified into more than two types, Sucrose-best (S-type) and MPG-best (M-type) fibers. Furthermore, each these fiber types could be classified into 2 groups, one type showing synergistic effect between MPG and IMP (S1, M1) and the other type showing no synergism (S2, M2). In the KO mice, S1-type was absent, but S2 and M2 types still remained. These data suggest that the information from umami receptor candidate T1R1/T1R3 may be mediated by transduction pathway including TRPM5 and carried by sweet taste sensitive nerve, and that specific umami taste information is mediated by other than T1R1/T1R3 and TRPM5 in mice. [J Physiol Sci. 2007;57 Suppl:S103]

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In many mammals, mirror-symmetric tonotopic organization of core fields in auditory cortex has been reported in electrophysiological and imaging studies. Studies in guinea pig auditory cortex have concluded that primary auditory field (AI) and dorsocaudal field (DC), the two core fields for guinea pigs, have mirror-symmetric tonotopy. This conclusion, however, is based in responses in the two fields to tones of a limited range of frequency. By using high-resolution imaging techniques with voltage-sensitive dye RH-795, we recorded responses in AI, DC, and several belt regions of anesthetized guinea pigs to tones of a broader range of frequencies, and examined the tonotopic organization of DC. In agreement with previous studies, DC had a tonotopy with a frequency axis in a caudal-to-rostral direction. Lower frequency tones activated a caudal part of DC and a rostral part of AI; these activated areas gradually approached each other with the increase of stimulus tone frequency. However, characteristic shapes of activation were observed in DC, according to tone frequencies. High frequency tones (12-24 kHz) activated a strip area, as reported in previous studies. Low frequency tones (0.25-1 kHz), however, activated a spot-like area. The area activated by middle frequency tones (2-8 kHz) was C-shaped, embracing the spot-like area activated by lower frequency tones. [J Physiol Sci. 2007;57 Suppl:S104]

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The molecular mechanisms coordinating cell cycle exit with cell differentiation and organogenesis are crucial, yet poorly understood, in the aspect of normal development of inner ear. The cell cycle is strictly regulated during development of inner ear to produce the correct number of sensory hair cells, supporting cells and neurons, which are required for hearing and balance function. It has been reported that the tumor suppressor phosphatase PTEN is essential for normal embryonic development, and PTEN expression is associated with cell cycle progression as well as neuronal differentiation. The aim of this study is to investigate the possible role of PTEN signaling during development of inner ear in mice. The results showed that PTEN began to express in the progenitor cells of cochleovestibular ganglion (CVG) neurons and progenitor cells of hair cells when the primordial organ of Corti exit from cell cycle by onset of p27kip1 expression. During the processes of hair cell differentiation, PTEN is expressed in the hair cells according to a spatial-temporal gradient. Inversely, p27kip1 expression is down-regulated in hair cells. After maturation of organ of Corti, PTEN becomes negative in hair cells and spiral ganglion neurons. In addition, in the PTEN+/- mice, the appearance of supernumerary hair cells was found when compared to the Wild-type mice. These findings suggested that PTEN may play a role in regulating the morphological development of inner ear [J Physiol Sci. 2007;57 Suppl:S104]

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In the retinal ganglion cells (RGC), various types of voltage-gated sodium channel (Na_v) α subunit mRNAs (Na_v1.1, Na_v1.2, Na_v1.3, and Na_v1.6) are expressed (Fjell et al., Mol Brain Res 50:197-204, 1997). Like RGC, subsets of retinal amacrine cells generate TTX-sensitive action potentials evoked by light stimulus, but subtypes of Nav expressed in these cells have not been identified. To examine the specific Na_v subtypes expressed in the retinal amacrine cells, we applied in situ hybridization (ISH) on the rat retina with the RNA probes that recognize TTX-sensitive Na_v (Na_v1.1, Na_v1.2, Na_v1.3, Na_v1.6 and Na_v1.7). We found that Na_v1.2, Na_v1.3, and Na_v1.6 were localized in the ganglion cell layer (GCL). Na_v1.7 showed weak and widespread expression in the retina. Interestingly, Na_v1.1 was expressed not only in GCL, but also in the inner nuclear layer (INL). Cell bodies of Na_v1.1-positive cells in INL were located on the INL/IPL (inner plexiform layer) border. Cell bodies of the AII amacrine cells are located close to INL/IPL border, and these cells can be labeled with antibodies to parvalbumin (PV). Therefore, we tried to combine ISH technique with immunohistochemistry. In most of Na_v1.1-positive cells located on the INL/IPL border, PV-immunoreactivity was observed. Our results suggest that at least Na_v1.1 is expressed in AII amacrine cells, while various types of Na_v are expressed in RGC. This difference in expression pattern might reflex functional difference of action potentials between these two types of cells. [J Physiol Sci. 2007;57 Suppl:S104]

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Odor identification and discrimination is often impaired in elderly adults. The underlying mechanism responsible for this change has yet to be uncovered. Discrimination and identification of odorants by the olfactory system is dependent upon the spatial mapping of different odorant receptors onto specific glomeruli in fixed locations within the olfactory bulb. To determine if the precision of the P2 odorant receptor map changes in old mice, we examined the olfactory bulbs of P2-IRES-tau-lacZ transgenic mice (ages 2 weeks-2.5 years) using X-gal staining to visualize the projections of P2 odorant receptor nerve fibers. For each glomerulus containing P2 axons, the amount of P2 labeling was classified as either full: > 90%; partial: 10-90% or trace: < 10%. Although there was no significant change in the number of "full" P2 glomeruli observed in old mice, there was a significant increase in the number of glomeruli with "trace" amounts of P2 labeling with the highest number observed in the oldest, 2.5 year old mice. Results from this study suggest that axon targeting and the precision of P2 mapping is altered in older adult mice. Alterations in odorant mapping could explain odorant identification impairment frequently observed in elderly adults. [J Physiol Sci. 2007;57 Suppl:S105]

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In barbiturate-anesthetized animals, primary auditory cortex (A1) neurons usually show onset responses for tonal stimuli. It is generally believed that A1 neurons do not have information of offset. However, offset responses are usual in A1 of awake animals and ketamine- and halothan-anesthetizad animals. We compared tonal offset responses with the onset responses in A1 of the awake animals. A majority of the neurons with phasic responses showed offset responses to tonal onsets, whereas only a small percentage of the neurons with sustain responses showed offset responses. The phasic neurons with on-off responses had different combinations of offset and onset frequency-receptive-field (FRF): offset-FRF was similar to onset-FRF, wider, narrower, higher or lower than onset-FRF. The offset-FRF pattern of each neuron was not changed at shift of the stimulation intensity and duration. At shift of the stimulus intensity response amplitude changed but not time parameters. Neuron-distribution pattern plotted by FRF-edge frequencies was diffuse, and pattern-boundaries were not found. The onset and offset responses fused at 50ms stimulus-duration. The offset responses were evoked whether the preceding inhibition was present or absent. The offset responses had a similar peak-latency, longer half-decay time and lower peak-amplitude than those of onset responses. In conclusion, the offset-FRF patterns are diverse. The offset responses are precise and salient when the tonal duration is > 50ms. The offset responses may be evoked by active mechanisms, but not passive rebound facilitation of a preceding inhibition. [J Physiol Sci. 2007;57 Suppl:S105]

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Not only painful sensation, but also itch is the sensation mediated by the unmyelinated C-fibers. We have performed two kind of analysis to evaluate the skin temperature changes induced by the C-fiber mediated-painful sensation using computer-assisted thermography. The first one is the analysis of the neurogenic inflammation. Intradermal injection of the algogenic substance such as the bee venom melittin increased the local skin temperature around the injection site, with a latency of a few minutes after on set of pain. The second one is to analyze the remote temperature in the index finger which is richly innervated by sympathetic vasoconstrictor nerves. Melittin injection into the forearm produced skin temperature decrease in finger, which was interpreted as a cutaneous vasoconstrictor reflex responses occurred simultaneously with pain sensation. Aim of the present study is to verify that the skin temperature changes are produced by itch stimulation similarly to painful stimulation. Although mechanical stimuli dose not usually evoke itch sensation for healthy subject, even the stimulation scratched the arm with a fingernail slightly evoked itch sensation for the healthy subjects but with dermography. Scratching stimulus produced the visible flare, vasodilatation and the skin temperature increase corresponding to these produced by the painful stimulation. However, it did not affect the finger temperature decrease. These results suggested that the stimulation which evoked itch sensation produced the axon reflex-neurogenic inflammation but not a cutaneous vasoconstrictor reflex responses. [J Physiol Sci. 2007;57 Suppl:S105]

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Nociceptive signals from the lower bowels are transmitted at two different regions in the spinal cord, the dorsal horn and the area around laminae VII and X. The present study examined the descending action from the locus coeruleus/subcoeruleus (LC/SC) on the transmission of nociceptive signals from the lower bowels at these two regions. Extracellular recordings from the spinal cord were made with a carbon filament electrode. Colorectal distention (80 mmHg) was produced by inflating a balloon inside the descending colon and rectum. Electrical stimulation of the LC/SC (30, 50 and 70 μA, 100 Hz, 0.1 ms pulses) was delivered either ipsilaterally or contralaterally. In neurons at both the dorsal horn and the area around laminae VII and X, nociceptive responses to colorectal distention were inhibited by LC/SC stimulation, and the inhibitory effect increased with the increase of LC/SC stimulus intensity. Following LC/SC lesions, LC/SC stimulation did not inhibit nociceptive responses, whereas inhibitory effects were observed by stimulation of the intact LC/SC contralateral to the recording site. These results suggest that the transmission of visceral pain at both two regions of the spinal cord is under the control of the centrifugal pathways from the LC/SC. [J Physiol Sci. 2007;57 Suppl:S106]

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The effect of CO₂/HCO₃⁻ on the endocochlear potential (EP) was examined by using both ion-selective and conventional microelectrodes and the endolymphatic or perilymphatic perfusion technique. The main findings were as follow: 1) A decrease in the EP from ∼+75 to ∼+35 mV was produced by perilymphatic perfusion with CO₂/HCO₃⁻-free solution, which decrease was accompanied by an increase in the endolymphatic pH (delta pH_e , ∼0.4). 2) Perilymphatic perfusion with a solution containing 20 mM NH₄Cl produced a decrease in the EP (delta EP, ∼20 mV) with an increase in the pH_e (delta pH_e, ∼0.2). 3) The perfusion with a solution of high or low HCO₃⁻ with a constant CO₂ level within 10 min produced no significant changes in the EP. 4) Perfusion of the perilymph with 10 μg/ml nifedipine suppressed the transient asphyxia-induced decrease in EP slightly, but not significantly. 5) By contrast, the administration of 1 μg/ml nifedipine via the endolymph inhibited significantly the reduction in the EP induced by transient asphyxia or perilymphatic perfusion with CO₂/HCO₃⁻-free or 20 mM NH₄Cl solution. These findings suggest that the effect of CO₂ removal from perilymphatic perfusion solution on the EP may be mediated by an increase in cytosolic Ca²⁺ concentration induced by an elevation of cytosolic pH in endolymphatic surface cells. [J Physiol Sci. 2007;57 Suppl:S106]

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Fos is a good marker for histological mapping of activated neurons in the central nervous system. However, its expression in the primary sensory neurons (PNS) is low and, therefore, cannot be used as a marker for activated PNS. In this study, we examined if phosphorylated nuclear factor kappa B (pNFkB) is a suitable marker for activated PNS. Male C57BL6 mice were injected with 20 μl of 10 mM capsaicin subcutaneously in the right hind paw under pentobarbital anesthesia. They were perfused from the left cardiac ventricle with 4% lidocaine 1 min, 5 min, or 15 min after the injection. Frozen sections of L4 DRG were triple-immunostained for pNFkB, capsaicin receptor (VR1), and neurofilament 200. At 1 min, pNFkB was observed in the nucleus of a subset of DRG neurons only in the injected side. At 5 min and 15 min, pNFkB-positive neurons appeared also in the contra-lateral DRG. The appearance of pNFkB-positive neurons in the contra-lateral side seems to be due to systemic spread of capsaicin because more than 90% of pNFkB-positive neurons were also positive for VR1 at all time points. In a separate group of mice, the right hind paw was electrically stimulated for 10 min, and their L4 DRG was examined for pNFkB. PNFkB-positive neurons were found only in the stimulated side and 45% of them were positive for VR1. These results suggest that pNFkB is a suitable marker for activated PNS. [J Physiol Sci. 2007;57 Suppl:S106]

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For electrophysiological studies of retinal ganglion cells (RGCs) in vivo, intraocular recording of RGC activity was well established in large mammals, such as cats and monkeys. However, the intraocular recording is technically difficult to be applied to rodents, because of their small eyeballs with large lenses. We here developed and validated a new method for in vivo recording of rat RGCs. Anesthetized adult rats underwent extracapuslar lensectomy and implantation of a imitation lens made from agarose. Thus, a tungsten microelectrode was easily inserted into the retina through the imitation lens for recording spike discharge of RGCs. A reference electrode was also inserted and situated in the lens. During the experiment, the eyeground was sporadically inspected for retinal detachment and/or ischemia. Retinas were able to keep up intact condition for several hours. Both single- and multi-unit activities of RGC were successfully recorded from not only the central but peripheral retinas with the electrodes which were three-dimensional micro-positioned. Spontaneous activities and responses to light stimulation of RGCs were recorded, in which the spike amplitudes of RGC activities were 90-400 μV. This method may be useful for in vivo electrophysiological studies of local impairments and recovery in the rat retinal function by various experimental manipulations, such as electrical stimulation, gene therapy, transplantation of stem cells and retinal prosthesis. Moreover, the technique might be applicable to studies in mice. [J Physiol Sci. 2007;57 Suppl:S106]

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It has been shown that noise can improve signal detection in nonlinear systems (Wiesenfeld & Moss, Nature 1995, 373, 33-36). Recently we have shown that contrast detection sensitivity in human visual perception can be improved by superimposition of visual noise (Sasaki et al. Neurosci. Lett. 2006, 408, 94-97). Here we examined the effect of noise on signal detection using a temporal two-alternative forced-choice (2AFC) paradigm. Nineteen undergraduate students (10 male, 9 female, mean age of 19.8 years) with normal or corrected to normal vision participated in this study. Participants were asked to detect signal of a small light spot (white LED) with its intensity modulated by sine waves at frequency of 1Hz. Random flickering light modulated by white noise was superposed on the signal. The performance rate of correct response was 62.6 ± 3.7% at control without noise, increased to 77.3 ± 2.3% (t(18)=2.738, p<0.05) at noise intensity of -10 dB (referring noise threshold as 0 dB), then decreased to 47.3 ± 4.3% at 20 dB (t(18)=-2.870, p<0.05). These results confirmed our previous findings that addition of appropriate level of noise can improve signal detection in human visual perception. [J Physiol Sci. 2007;57 Suppl:S107]

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It is generally believed that tuning properties to stimulus orientation (orientation selectivity) emerges first at the primary visual cortex (V1). In the present study, we recorded neurons of the lateral geniculate nucleus (LGN) of anesthetized cat and found that more than 90% of LGN neurons exhibited significant orientation selectivity under stimulus condition with higher spatial frequency and larger size than the optimal. From our experimental results, the receptive fields of LGN neurons are suggested to be elongated along the axis parallel to their preferred orientation. Mean aspect ratio of elliptical receptive field of most LGN neurons is more than 1.5. Additionally, we measured the area-summation curves of neuronal responses with gratings of optimal and orthogonal to the optimal (null) orientations, and found that the degree of surround suppression in LGN was significantly stronger at null orientation than at optimal orientation. This result suggests that orientation-tuned surround suppression enhances orientation tuning of LGN neurons under large stimulus condition. With a presence of surround suppression, orientation-tuning property already appears at the level of LGN, which could be an origin of cortical orientation selectivity in cat. [J Physiol Sci. 2007;57 Suppl:S107]

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Metacontrast masking is a phenomenon that the visibility of a briefly presented stimulus (target) is reduced by a spatially adjacent and temporally delayed brief presentation of stimulus (mask). In our previous psychological study in human, we reported that the magnitude and stimulus tuning property of metacontrast effects changed dynamically depending on the stimulus onset asynchrony (SOA). The selectivity to stimulus parameters such as stimulus orientation and spatial frequency was higher at short SOAs (0-40 ms) than at long SOAs (80-100 ms), suggesting the existence of distinct mechanisms with different spatiotemporal properties. In order to identify regions in the human cortex that may provide the neural basis of metacontrast masking, we investigated the correlation between a perceptual detectability of a target and BOLD signals by combining the psychophysical test and the event-related functional magnetic resonance imaging (fMRI). We examined the effect of orientation contrast between target and mask (iso-oriented vs. cross-oriented masks) and its dependency on SOAs (-120, 0, 80, 200 ms). In group analysis, we found significant signal changes between two orientations in lingual gyrus (Brodmann area 19), premotor cortex (Brodmann area 6) and inferior parietal lobule (Brodmann area 40). Now, we are analyzing BOLD signals in these areas to quantify the SOA dependency and the interaction between orientation and SOA in relation to psychological performance of subjects. [J Physiol Sci. 2007;57 Suppl:S107]

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Biological signal transduction is conducted frequently at very fine cell structure expressing nano-level compartments. Up to this point, however, physiological experiments treating such fine structure are limited, mainly because of technical limitations. To overcome difficulties, we employed a combined a patch clamp and photolysis of caged compound under fine visualization of sub-micron structure with the laser-scanning confocal microscope. We used olfactory cilia as an example having 100 nm diameter structures. Our aim is to obtain real time dynamics of molecular elements in living cell with a high spatial resolution. Cilia were loaded with both caged cAMP for photolysis and lucifer yellow for luminescent visualization. When the laser light for photolysis is collected at the focal plane with the objective lens, the size (D) of the laser spot is determined following the relation, D ∝λ/NA. To obtain a small spot for a high spatial resolution, we used a objective lens having a large NA (1.4) and a short wavelength light (λ=364 nm). If the intensity of the UV spot is assumed to express spatially a two-dimensional Gaussian distribution, σ was estimated experimentally to be <300 nm. The On-Off and position of the UV spot were regulated by AOTF device and Galvano-mirror. When the local area (ca. 1 μm length) of cilium was illuminated under the whole-cell voltage clamp(-50 mV), the cell showed an inward current response of ∼10 pA, caused by the local and sudden increase of the cytoplasmic cAMP. We describe response generation, adaptation, kinetics and spatial distribution of the cAMP-triggered machinery. [J Physiol Sci. 2007;57 Suppl:S107]

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A cochlear extracellular fluid, endolymph, has 150 mM K⁺ and positive potential of ∼+80 mV called "endocochlear potential (EP)". EP is essential for hearing. K⁺-transport via an epithelial tissue "stria vasclularis" in the lateral wall is crucial for maintaining the high K⁺ and EP. Stria vascularis comprises marginal (MCs) and intermediate (ICs) cells. The extracellular space sandwiched by the two is referred as "intrastrial space (IS)" and harbors low K⁺ of ∼2 mM and high potential of ∼+90 mV. This unique property is proposed to be an origin of EP and achieved by cooperation of Na⁺,K⁺,2Cl⁻-cotransporter (NKCC) and Na⁺,K⁺-ATPase at the basolateral membrane of MCs and K⁺ channel at the apical site of ICs. However, the mechanism for its establishment is unknown. We thus measured the potential and K⁺ concentration ([K⁺]) of IS with a double-barreled electrode while applying furosemide, a NKCC-blocker, and anoxia, which dysfunctions Na⁺,K⁺-ATPase. Strial perfusion of furosemide largely declined the potential and increased [K⁺] in IS as well as reduced EP. Anoxia caused the same effect. The amplitude of change in IS-potential and EP paralleled that in K⁺ equilibrium potential toward IS. Hence, low [K⁺] in IS maintained by NKCC and Na⁺,K⁺-ATPase in MCs may promote [K⁺] diffusion via K⁺ channel in ICs, which forms IS potential and EP. [J Physiol Sci. 2007;57 Suppl:S108]

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It is known that L-γ-Glutamyl-L-cysyeinylglycine (GSH), a tripeptide with glutamic acid, cysteine and glycine, increases flavor characteristics of an umami solution containing each of monosodium glutamate (MSG) and 5-inosine monophosphate (IMP) in human (Ueda et al., 1997). In this study, we conducted behavioral and electorophysiological experiments to investigate the neurophysiological characteristics of GSH for the taste receptor by using C57BL/6 mice. In the behavioral study, preference percent for IMP mixed with GSH was higher than that for pure IMP. But mixing of GSH did not change the preference percents for MPG and binary mixture of MPG and IMP. In the electrophysiological study, when GSH was mixed with IMP, the chorda tympani nerve response showed strong synergistic effect. But mixing of GSH did not increase the response to MPG. The response of mixture of MPG and IMP was cross-adapted by that of GSH + IMP in the chorda tympani nerve. It is possible that GSH attacks the site for glutamate and make synergistic effect with IMP. [J Physiol Sci. 2007;57 Suppl:S108]

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In the frog taste disc, wing cells, but not rod cells display inward currents in response to external arachidonic acid (AA). In the present study, we investigated the biophysical properties of lipid mediator-induced currents while recording the whole cell currents of isolated rod and wing cells in frog taste discs. When AA (50 μM) was applied extracellularly, the wing cells displayed parabolic inward currents. The current conducted poorly at the membrane potential of -80 mV despite the presence of AA, but their conductance increased at a resting potential of -50 mV. AA (50 μM) elicited inward currents of -40 ± 9 pA (N=10) in the wing cells. Linoleic, linolenic and docosahexaenoic acids induced similar currents in the wing cells. Although the rod cells display only enhancement of the outward currents in response to external AA, intracellular dialysis with 50 μM 1-oleoyl-2-acetyl-sn-glycerol (OAG), a synthetic analog of diacylglycerol (DAG), induced inward currents of -155 ± 36 pA (N=4) at -50 mV in 4 of 6 rod cells. I-V relationships of OAG-induced currents were almost linear. The wing cells did not respond to internal OAG. The results suggest that frog rod and wing cells may have different roles in taste transduction. [J Physiol Sci. 2007;57 Suppl:S108]

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Phenylthiocarbamide ( PTC ) is extremely bitter substance for most people but the compound is tasteless or slightly bitter taste for some people. The former are called tasters for PTC and latter non-tasters for PTC. We measured thresholds to phenylthiocarbamide ( PTC ) in the students, aged 19 to 37, in Nagasaki University School of Dentistry. The percentage of non-tasters for PTC was 10.9% in 110 dental students. The distribution of non-tasters was 11.8% in 51 female students and 10.2% in 59 male students. We also investigated the electric taste-sensitivity on six regions of oral cavities using electrogustometry in the same students. The electrogustometric sensitivity between on the soft palate and the posterior region of the tongue was significantly different in tasters and non-tasters. We found that non-tasters were higher electrogustometric sensitivity on the soft palate than the posterior region of the tongue. [J Physiol Sci. 2007;57 Suppl:S108]

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Preference of infants for human faces is presumably of great importance for later development of social cognition. Human faces contain various types of information, of which emotional facial expression and gaze direction are particularly important. In the present research, we determined whether gaze directions influence discrimination of emotional facial expressions in infants. In order to assess their ability, we measured the latency to disengage their attention from face stimuli presented at the center of their visual field. The face was posing either happy or angry facial expression, and the gaze was directed either straight to or averted from the viewers. At the start of each experimental trial, a human face was presented. When the infants fixated on the face, the geometrical target was presented at the periphery of their visual field. We measured the latency of infants to make a saccadic eye movement to peripheral target, and compared the SRTs (saccadic reaction time) across Gaze Direction (2) x Facial Expression(2) = 4 experimental conditions. The longer the SRT was, the more effectively the face stimuli captured attention of infants. The analysis revealed that SRT was significantly longer for angry faces than for happy faces when the gaze of the stimulus face was looking straight, while no such tendency was found when the gaze of the stimulus face was averted. The indications of this finding are discussed in the context of the development of visual attention and social cognition during infancy. [J Physiol Sci. 2007;57 Suppl:S109]

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Multiple-site optical recording of neural activity provides a powerful tool for the cerebral cortical neurophysiology. However, to detect the membrane potential optically from the intact cortex, reflected-light fluorescence method must be used and the optical signal usually has low signal-to-noise (S/N) ratio and requires summation. Therefore, the application of the optical recording of the membrane potential to the cortex has been restricted to reproducible, stimulus-evoked activation. We have developed an optical recording system suitable for detecting on-going cortical activity, with high S/N ratio enough for single-sweep analysis, by using fiber optics as the excitation light source, and applied this system to the intact rat cortex. The sensorimotor region was exposed and stained with a voltage sensitive dye (RH414) without peeling dura. The electroencephalogram (EEG) was recorded simultaneously with an electrode placed in the optical monitoring area. Deflections time-locked to large, irregular EEG activities emerged in the optical recording after the pulsation artifacts were largely reduced by software. The optical signal was distributed over a broad region, whose time course, amplitude or shape varied within the region with slight differences in the onset time. This possibly reflected regional differences of the neural activities in the cortex which produced the EEG transient. Thus, our system could be a powerful tool to study spatial organization of spontaneous cortical activities. [J Physiol Sci. 2007;57 Suppl:S109]

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To evaluate a mechanism underlying Dan Tian (DT) Breathing, We investigated regional activation in the parietal and frontal cortices as assessed by changes of hemoglobin oxygenation during electrical or mechanical stimuli on (DT) using 24-channel near-infrared spectroscopy NIRS) in heathy subjeacts.During electrical stimulation of DT for 2 minutes, the levels of oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (deoxyHb) decreased temporarily in the parietal regions near the Cz portion and the primary motor cortices. By contrast, electrical stimulation on the right forefinger elicited an increase or no change of oxyHb in the above regions. On the other hand, oxyHb concentration reduced markedly in the prefrontal cortex during mechanical stimulation of DT, though a small decrease in oxyHb was observed during mechanical stimulation of the forearm. These results suggest that DT stimulation causes active inhibition of pefrontal cortex and medial parietal part of parietal cortices. [J Physiol Sci. 2007;57 Suppl:S109]

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Retinal amacrine cells (ACs) regulate activities of retinal ganglion cells, the output neurons to higher visual centers. Homologous electrical synapses between ACs contribute cellular mechanism of lateral inhibition in the inner plexiform layer. Lateral inhibition was expected to depend on functional coupling by electrical synapses. The fraction of open channels in gap junction plaques was evaluated with techniques of dual patch-clamp recordings, intracellular labeling, connexin immunocytochemistry, and high-voltage electron microscopy. Electrical junction conductance in cell pairs was measured by dual patch-clamp recordings. High voltage electron microscopy (Hitachi 1250M, NIPS, Okazaki, co-operative program 2006-HVEM13) measured the size of gap junction plaques localized between the dendrites of Neurobiotin-coupled cells. In confocal laser-scanning imaging, connexin localization counted homotypic gap junction connections. Assuming the density of connexons by freeze-fracturing methods and measured single channel conductance, the conductance of each gap junction plaque was expected. The presence of junctional connections between a cell pair will lead to estimate a total intercellular junctional conductance. The measured conductance could allow to estimate a fraction of functional channels in a gap junction plaque. The open channel fraction may be on the order of 1 in 10, which was compatible to that of alpha retinal ganglion cells (Hidaka et al., J Neurosci, 24, 2004). [J Physiol Sci. 2007;57 Suppl:S109]

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In the central nervous system, histamine is known to act on three major types of G-protein-coupled receptors; histamine receptor 1 (HR1), histamine receptor 2 (HR2) and histamine receptor 3 (HR3). HR1 has been characterized in mammalian retinas. HR2 typically activated the signaling pathway. Histamine increased a GABA-mediated chloride current in amacrine cells from rat retinal slices via protein kinase A. Histamine via HR3 inhibited electrically-evoked dopamine release from the pig retina. Through electron microscopic technique and immunocytochemical staining methods, the localization of HR3, mGluR6 and GABA became apparent in ON-bipolar cell dendrites of the macaque retina, while HR1 and TH were localized in dopaminergic amacrine cells in the rat retina (Matthew et al., 2006).The gerbil is the animal which is characteristic to the central retinal artery. We have examined the localization of the histamine receptors in the gerbil retina using immunocytochemical method. The gerbils were perfused intracardially with a mixture of 4% paraformaldehyde in 0.1M sodium phosphate buffer. After the removed eyeballs were frozen with the rapid liquid nitrogen, they were cut with section of 10 μm using a cryostat. Experiments were performed to identify the targets of histaminergic retinopetal axons. We report the localization of histamine receptors in gerbil retinas by using light microscopic immunolabeling techniques. [J Physiol Sci. 2007;57 Suppl:S110]

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In the widely divergent species, GABA neurons make widespread connections within neuronal networks and thus are capable of controlling network oscillations and their patterns. In the terrestrial mollusk Limax valentianus, oscillatory activity of the procerebrum (PC) neurons is considered to encode the odor information. Previous studies of immunohistochemistry and electrophysiology showed that GABA is present in the CNS and may be involved in the odor information processing of Limax. In the present study, we have applied immunohistochemical methods to the sectioned preparations of Limax CNS to identify GABA-like immunoreactive neurons and to assess the spatial patterns of innervations by these cells in the CNS. The neuronal cell bodies and fibers showing GABA-like immunoreactivity were distributed widely throughout the CNS, and they were also extensively observed near the PC lobes. Then, we examined the GABAergic effects on the generation of local field potential (LFP) in the PC lobes and the GABAergic effects on the neuronal activity in the PC neurons. Application of GABA-receptor antagonists to the whole CNS decreased the frequency of the oscillatory neural activity as a periodic LFP. On the other hand, application of GABA-receptor agonists increased or decreased the LFP frequency. These results suggested that the GABAergic synaptic transmission is involved in the oscillatory neural network of the PC in Limax and may play excitatory roles in the LFP generation. [J Physiol Sci. 2007;57 Suppl:S110]

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Gap junctions are found in neuroepithelial cells in the early embryonic retina (Fujisawa et al., 1976). However, the gap junction disappears as the retinal cells differentiate and the functional role of the gap junction in the early retinal development remains unknown. In the present study, the electrophysiological properties of the retinal neuroepithelial cells were investigated by intracellular recordings in an isolated preparation of the retinal neuroepithelium dissected from embryonic day 3 (E3) chick. The retinal neuroepithelial cells showed resting membrane potentials of -63 to -89 mV. Input resistances were measured by passing steady depolarizing and hyperpolarizing currents of 0.2 nA. The input resistance ranged from 14 to 80 Mohm. No evidence for conventional action potentials was found even with a depolarizing current of 1.0 nA. Carbenoxolone (CBX), a gap junction channel blocker, was applied to the retinal neuroepithelium during the intracellular recording. The input resistance was remarkably increased by the application of CBX; 10 μM of CBX increased the input resistance by 2-4 times and 100 μM of CBX increased it by 5-6 times. The resting membrane potential became unstable and shifted in depolarizing direction with CBX. Alexa Fluor 488 hydrazide (MW: 570.48) was injected into the cell by passing hyperpolarizing current pulses through the recording electrode. The injection of Alexa Fluor 488 revealed clear dye coupling. These results suggest that the gap junctional coupling between the retinal neuroepithelial cells lowers the input resistance and stabilizes the resting membrane potential of the neuroepithelial cell. [J Physiol Sci. 2007;57 Suppl:S110]

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Although it is widely accepted that visual and vestibular (mainly otolith) systems affect tilt perception, the contribution of somatosensory system to the tilt perception is still unclear. To investigate the influence of somatosensory inputs from lower limb on the tilt perception, subjective visual vertical (SVV) and head stability were measured during upright standing on the platform tilted to the right (0, 3, 6 and 9 degrees) under the dark in five healthy subjects (22-32 years) for over 3 minutes. The values of SVV (between -1.5 and 3.5 degrees) and the head tilt (between -2.5 and 3.5 degrees) were small and they had almost no relationship to the platform tilt: the correlation coefficients were 0.15 (p>0.18) and 0.13 (p>0.21), respectively. On the other hand, the correlation coefficients between the SVV value and the head tilt at 0, 3, 6 and 9 degrees of platform tilt were -0.17 (p>0.32), 0.06 (p>0.50), 0.53 (p>0.10) and 0.75 (p<0.02), respectively. These results indicate that the SVV (=the tilt perception) is determined by the combination of the platform tilt (=the somatosensory inputs from lower limb) and the head tilt (=the vestibular and/or the neck somatosensory inputs). [J Physiol Sci. 2007;57 Suppl:S110]

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This study investigated the hypothesis that activation of satellite glial cells modulates the excitability of trigeminal ganglion (TRG) neuronal activity via an IL-1β following inflammation. Two days post-CFA injection, the mean percentage of TRG neurons encircled by glial fibrillary acidic protein (GFAP)- / IL-1β-immunoreactive cells was significantly increased compared to controls. GFAP and IL-1β immunoreactivities were co-expressed in the same cells. Fluorogold (FG) labeling identified the site of inflammation. The number of FG-labeled IL-receptor type I (IL-1RI) TRG neurons in inflamed rats was significantly greater than in controls. In FG-labeled small TRG neurons, the size of IL-1β (1 nM) induced-depolarization in inflamed rats was larger than in controls. IL-1β application significantly increased firing rates evoked by depolarizing pulses in the neurons of inflamed rats,compared to controls. Inhibition of voltage-dependent K⁺ currents by IL-1β application in inflamed rats was significantly larger than in control. The responses of TRG neuronal activity to IL-1β were abolished by treatment with the IL-1RI antagonist. These results suggest that activation of satellite glial cells modulates the excitability of small-diameter TRG neurons via IL-1β following inflammation, and that the up-regulation of IL-1RI in the soma may contribute to the mechanism underlying inflammatory hyperalgesia. [J Physiol Sci. 2007;57 Suppl:S111]

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Trigger points (TPs) are specific areas in the muscle, where characteristic symptoms such as referred pain are induced by pressing on those areas, and have been used to diagnose chronic pain syndrome such as myofascial pain syndrome and fibromyalgia. Acupuncture has been applied to TPs for treatment of chronic pain syndrome to induce specific sensation (de-qui: soreness, numbness, heaviness, and fullness), which has been used to assess effectiveness and adequacy of acupuncture stimulation. In the present study, we investigated relationships between de-qui sensation and cerebral hemodynamic responses using near infrared spectroscopy (NIRS). Acupuncture needle was inserted into the TPs of the right extensor muscle, and acupuncture manipulation (back-and-forth vertical movement) was applied for 8 trials of each 15 sec. The subjects were required to press a button when they felt de-qui sensation. The results indicated that Oxy Hb concentration was significantly decreased in the bilateral supplementary motor areas, compared with needling without any specific sensation. Previous studies reported that excessive motor outputs are one of causes of various chronic pain syndromes. The results suggest that acupuncture might ameliorate chronic pain by decreasing motor outputs. [J Physiol Sci. 2007;57 Suppl:S111]

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Relationships between neuronal activities and hemodynamic responses remain unknown. We recorded simultaneously hemodynamics (Oxy-, deoxy-, and total-Hb tissue concentration) by NIRS and EEGs from the whole brain, while human subjects received the right median nerve electrical stimulation. Stimulus frequencies varied form 2 to 10 Hz. The 3-D coordinates of the NIRS probes and EEG electrodes were stereotaxically measured. Statistical significance of hemodynamic responses was evaluated by general linear model (GLM). The resultant NIRS and EEGs data were stereotaxically superimposed on the reconstructed brain of each subject. EEG data indicated that typical somatosensory evoked potentials (N21) were recorded from the contralateral somatomotor cortex. The NIRS data indicated that Oxy-Hb concentration increased at the contralateral SI area and then the responses spread to more posterior and ipsilateral areas. Comparison of these 2 data indicated that; (1) 3-D distance between dipoles of N21 and position of the channels with maximum Oxy-Hb responses was less than 10 mm, (2) the 2 topographical maps of NIRS and EEGs were significantly correlated. These results suggest usefulness of simultaneous recording of NIRS and EEGs. [J Physiol Sci. 2007;57 Suppl:S111]

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In the oral cavity, L-glutamate confers umami taste via transduction pathways of metabotropic glutamate and T1R receptors in taste cells. This taste quality induces cephalic phase responses, reflex-like consummatory behavior and conveys nutrient information to the brain. Recent work has shown that chemosensation is not restricted to taste tissue. The gastrointestinal (GI) tract also responds to chemical signals in the lumen. We reported that L-glutamate in the stomach lumen activates gastric afferent fibers of the vagus nerve. And this response is specific to L-glutamate. Other amino acids do not stimulate vagal afferent fibers from the gastric branch. However, the precise molecular processes for this activation are still unknown. Taste related proteins such as the a-subunit of gustducin, the transient receptor potential TRPM5 or T2R bitter taste receptors have been already described in the GI tract. Likewise, several umami receptors have the potential to mediate this stimulation of the vagus nerve. Yet, among them, mGluR1 is the only excitatory glutamate receptor with a high specificity for L-glutamate in the rat. We investigated in the present study the expression and distribution of mGluR1 in the gastric mucosa, and tested the effect of L-glutamate in stomach function. [J Physiol Sci. 2007;57 Suppl:S111]

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We previously demonstrated that the canine nociceptor response to bradykinin (BK) was sensitized by agonist of prostaglandin receptor EP3 and decreased by cAMP-increasing reagents. In Chinese hamster ovary cells expressing EP3 cloned from canine dorsal root ganglia and mouse BK B2 receptor, we examined the effects of EP3 agonist, ONO-AE-248, and a specific inhibitor of protein kinase A (PKA), H-89, on the [Ca²⁺]_i increase induced by BK. When BK (1 nM) was applied twice with a 6-min interval, the second response (maximal [Ca²⁺]_i increase) was markedly attenuated to approximately 50% of the initial one. ONO-AE-248 (0.1 μM) significantly restored this attenuation to more than 80% in a PTX-sensitive manner without inducing any change in [Ca²⁺]_i by itself. The pretreatment with H-89 (1 μM) also restored the second response. Both reagents had no effect on the initial BK response. These results demonstrate that BK-induced desensitization of BK B2 receptor is a slower event than the BK-induced [Ca²⁺]_i increase and that the activation of EP3 restores the response to BK by attenuating the BK-induced desensitization of BK B2 receptor through activation of Gi protein and thus downregulation of PKA. [J Physiol Sci. 2007;57 Suppl:S112]

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There are many studies measuring the mechanical withdrawal threshold (MWT) in animals with Randall-Selitto (RS) apparatus, however, it is not clear which tissue's threshold RS device measures. In our previous human experiment with surface anesthesia, we showed that a probe larger than 2 mm measured the pain threshold of deep tissues (possibly muscles) while a smaller probe measured the skin pain threshold. To know the influence of probe diameter on the depth of tissues MWT of which the RS apparatus measures, we examined two probes of different diameters (normal probe with tip diameter 1.3 mm originally attached to the RS device and modified probe with tip diameter 2.6 mm made by our lab), and effect of surface anesthesia (EMLA cream containing 2.5% lidocaine and 2.5% prirocaine, for 30 min) on MWT measures with these probes. For comparison, MWT was also measured with von Frey hair (VFH, 0.5 mm tip diameter). SD rats (n=27) were used in this study. Surface anesthesia increased the MWT measured with von Frey hairs and that measured with the normal probe-equipped RS device. In contrast, MWT measured with the larger probe-equipped one was not influenced by surface anesthesia. These data demonstrated that the WMT measured with VFH and normal probe-equipped RS device reflects the cutaneous pain threshold while that measured with larger probe-equipped RS apparatus reflects the pain threshold in deep tissues. [J Physiol Sci. 2007;57 Suppl:S112]

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Previously we showed the existence of tenderness (DOMS) after lengthening contraction (LC) by nocifensive behavioral tests and c-Fos protein expression in the spinal dorsal horn in rats. The mechanical withdrawal threshold of the EDL muscle underwent LC decreased 1 day after LC and remained decreased up to 3 days after LC. It returned to the pre-LC value 4 days after LC (Taguchi, 2005). To know if inflammatory mediators are involved in DOMS, we examined effects of NSAIDS and BK receptor antagonists. We used two selective COX2 inhibitors, Zaltoprofen (additionally having BK blocking effect) and Celecoxib, and BK receptor antagonists (des-Arg-HOE 140 : B1 receptor antagonist, HOE-140 : B2 receptor antagonist). We administered these drugs 1 hr (NSAIDS, p.o.) or 0.5 hr (BK antagonists, s.c.) before LC and 2 days after LC. Zaltoprofen and Celecoxib (10 mg/kg) administered before LC blocked the development of the mechanical hyperalgesia, but failed to reverse the developed mechanical hyperalgesia when administered 2 days after LC. Zaltoprofen was effective at a lower dosage (5 mg/kg) than Celecoxib (10 mg/kg). Administration of HOE-140 before LC inhibited the development of mechanical hyperalgesia but des-Arg-HOE 140 did not. Both drugs failed to reverse the mechanical hyperalgesia when administered 2 days after LC. These results suggest that prostaglandins and BK through B2 receptor are involved in the development of mechanical hyperalgesia but not in its maintenance. [J Physiol Sci. 2007;57 Suppl:S112]

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Objective: Effect of estrogen content on the development of delayed onset muscle soreness (DOMS) was examined in the ovariectomized rats. Methods: A total of 18 female rats [36 legs] were allocated to three groups. Control [CG, n=6], eccentric exercise [EEG, n=6] and exercise under ovariectomy [OVX, n=6]. Estrus cycle of each rat was determined by the smear test in blinded manner. These procedures were performed on the gastrocnemius [GS] muscle. Pain thresholds were measured daily by von Frey test [VFT] and Randall-Selitto test [RST] over the GS muscle for 1 week after the conditioning stimulation. Results: The thresholds of VFT and RST kept stable in the CG. during the experimental period, although the lowering of RST threshold was observed in the estrus period. In the EEG, the thresholds of RST of the exercised side were the lowest on the 1st day after exercise and returned on 7th day. No influence was observed in the contralateral side. In the OVX, however, the decrement of RST threshold of the exercised side was delayed and the lowest value was on the 2nd day after the exercise and returned on 7th day. The VFT thresholds were not changed significantly in the EEG and OVX. Conclusion: In the present study, the delay of development of muscular hyperalgesia was detected in the OVX rats. This result suggests that the change of estrogen content might to be a possible cause of muscle pain. [J Physiol Sci. 2007;57 Suppl:S112]

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There are numerous clinical evidences on the analgesic effect of acupuncture and moxibustion (mox) for OA, however its action mechanism has not been clarified. The purpose of this study was to investigate the effect of indirect mox on the knee OA model in the rat. Male Wistar rats (n=20, 296-421g) were used. Experimental OA was induced by injection of mono-iodoacetate (MIA) (3mg, 50 μl) into the knee joint. Animals were divided into mox and control (non treatment) groups. Rats in the mox group received a single indirect mox on the lateral side of ipsilateral joint for 28days every other day. Pain related behavior was measured using a hind limbs weight. Percentage of the ipsilateral limb weight of total hind limbs weight was calculated. In the control group, a significant decrease of% weight in ipsilateral limb continued for 14days post injection. On the other hand, a significant decrease in ipsilateral limb lasted for 7days in mox group. In the initial 7 days, no apparent difference between the control and mox groups were observed. Area under the curves (AUC) of baseline in both groups were calculated during 28 days after MIA injection. The AUC in the mox group was significantly smaller than that of control group. In this study, indirect mox has a potential to reduce the osteoarthritis pain after 7 days of repetitive treatments. This kind of slowly developed analgesic action of mox is similar to those of in the clinical situation and the underlying mechanisms will be discussed. [J Physiol Sci. 2007;57 Suppl:S113]

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The processing of spectral and temporal information in the core fields of the left and right auditory cortices of the guinea pig was investigated using optical imaging with a voltage-sensitive dye (RH795). Seventeen guinea pigs were anesthetized with ketamine (80mg/kg) and xylazine (40mg/kg). In order to compare the functional difference between the left and the right auditory cortex, optical imaging patterns to repeated sound ( tone, click, harmonic noise and native sound (Qui sound)) at different repetition rates (4-20 Hz) were recorded from core auditory fields (primary (AI), dorsocaudal (DC) fields) of both sides. Repetition rate transfer functions (RRTF) in field AI were low-pass showing a sharp drop-off in evoked activity per click or noise above 10 Hz but RRTFs in field DC were bandpass with the peak of 8 or 10 Hz. The cut-off frequencies of RRTF in the left cortex were the same as those in the right cortex but the slopes of the RRTF in the left cortex were sharper. On the other hand, The slopes of RRTF per tone or Qui sound in field AI of the wider cortex were gentler than those in the narrower one. We discuss the functional difference between the left and right auditory cortices of guinea pigs. [J Physiol Sci. 2007;57 Suppl:S113]

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In the present study, the activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK) in the rostral ventromedial medulla (RVM) following the injection of complete Freund's adjuvant (CFA) into the rat hindpaw was examined in order to clarify the mechanisms underlying the dynamic changes in the descending pain modulatory system after peripheral inflammation. Phospho-ERK-immunoreactive (p-ERK-IR) and phospho-p38 MAPK-immunoreactive (p-p38 MAPK-IR) neurons were observed in the nucleus raphe magnus (NRM) and nucleus reticularis gigantocellularis pars alpha (GiA). Inflammation induced the activation of ERK in the RVM, with a peak at 7 hours after the injection of CFA into the hindpaw and a duration of 24 hours. In the RVM, the number of p-ERK-IR neurons per section in rats killed at 7 hours after CFA injection (14.2±1.7) was significantly higher than that in the control group (4.5±0.9) (p<0.01). In contrast, activation of p38 MAPK in the RVM was observed within 1 hour after CFA injection. After CFA injection, about 60% of p-ERK-IR neurons, about 40% of p-p38 MAPK-IR neurons in the RVM were serotonergic neurons. The p-ERK-positive rate of RVM serotonergic neurons in the rats with inflammation was seven times higher than that in control rats (p<0.01). These findings suggest that inflammation-induced-activation of ERK and p38 MAPK in the RVM may be involved in the plasticity in the descending pain modulatory system following inflammation. [J Physiol Sci. 2007;57 Suppl:S113]

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Little is known about how temporal interactions of sensory inputs of different modalities affect thalamic information processing. We examined effects of temporal interactions between auditory and somatosensory inputs on thalamic cell activity, based on c-Fos expression induced by pure tone bursts (frequency, 8 kHz; duration, 200 ms) and/or foot shock stimuli (intensity, 1.0 mA; duration, 500 ms). Five sets of auditory and somatosensory stimuli (inter-set interval, 5 min) were given to awake rats with the following sequences in a set: 1) ten pure tone bursts (interval, 800 ms) and a foot shock stimulus immediately after the tone bursts (A-S, n = 6), 2) a foot shock stimulus and ten tone bursts immediately after the shock stimulus (n = 6), 3) tone bursts either before or after a shock stimulus (pseudo-random, n = 6). Additionally, only pure tone bursts (n = 5) or foot shock stimuli (n = 6) were given. Animals were euthanized with Nembutal (i.p.) at 90 min after the sensory stimuli, and brains were processed to reveal c-Fos expression. c-Fos positive cells were counted in the dorsal (MGD), ventral (MGV) and medial (MGM) divisions of the medial geniculate body and the suprageniculate nucleus (SG). In the MGD and MGV, the number of c-Fos positive cells was significantly large in A-S group as compared with those in the other groups. In the MGM and SG, there was no significant difference in the degree of c-Fos expression among the groups. The results suggest that a specific temporal interaction is crucial for cross-modal sensory integration in the thalamus. [J Physiol Sci. 2007;57 Suppl:S113]

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In the rat auditory cortex, ventral (V) and posterodorsal (PD) areas are the two major auditory fields that receive thalamic afferents from the dorsal division (MGD) of the medial geniculate body. V and PD are presumed to serve distinct functions in tandem as the pair of major cortical recipients of extralemniscal thalamic inputs. To deduce the functional significance of V, efferent connections of V were examined with the anterograde tracer biocytin. V extends primarily in the ventral margin of area Te1. Biocytin was iontophoreticallcy injected into cortical regions, which were defined as V based on histological location, auditory response and thalamocortical connectivity. Anterograde labeling revealed two important aspects of cortical projections. First, V sent a projection to a well-confined region in the caudal end of the insular cortex (Ins) pivotal for fear memory formation during aversive conditioning. Second, V sent parallel projections to cortical regions that likely comprise the other non-primary auditory fields, including PD. The results suggest that V relays auditory input from the MGD to the Ins for affective memory formation and at the same time dispatches the auditory input, which could be weighed as emotional content, to the rest of non-primary auditory fields. PD is assumed to play a pivotal role in auditory spatial processing for directed attention. As the counterpart of PD, V is assumed to give rise to another major stream of cortical information processing most likely related to emotion. [J Physiol Sci. 2007;57 Suppl:S114]

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We previously reported that mast cell surface antigen-1 (MASA-1) is specifically expressed on mast cells from day 3 following antigenic stimulation in a rat type I allergy model. In addition, expression of MASA-1 on a human mast cell line, HMC-1, was up-regulated by TGF-β1 and TNF-α. However, expression of MASA-1 during the course of the differentiation of mast cells is unclear. To investigate the mechanism of MASA-1 expression, bone marrow cells from NC/Nga mice were cultured for 8 weeks in the presence of SCF and IL-3 in order to differentiate bone marrow derived mast cells (BMMC), and followed by FACS analysis. The frequency of metachromatic cells was 89% at 4 weeks and 78% at 8 weeks of culture. Furthermore, many cultured bone marrow cells expressed both FcεRI and c-kit (82.6 ± 1.8 and 75.4 ± 2.3%, at 4 and 8 weeks of culture). However, the percentage of MASA-1⁺c-kit⁺ cells was less than 2.5% at 4 weeks of culture, while MASA-1 was weakly expressed on BMMC at 8 weeks of culture (11.3 ± 1.8%). The 4-week culture of BMMC was then treated with TGF-β1, and cultured for another 4 weeks. TGF-β1 did not induced MASA-1 expression on BMMC. The percentage of MASA-1⁺c-kit⁺ cells on BMMC co-cultured with fibroblasts derived from NC/Nga skin was nearly identical to that of BMMC at 8 weeks culture. These results show that MASA-1 is not markedly expressed during the course of maturation. Analysis of regulatory mechanisms of MASA-1 expression on mast cells is currently in progress. [J Physiol Sci. 2007;57 Suppl:S114]

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Parkinson disease (PD) is reported to be caused by an interaction between genetic and environmental factors. Fewer studies clarified environmental factors. Rotenone, a pesticide, is recently highlighted because rotenone treatment to animals produces many features of PD including behavioral abnormalities, selective degeneration of nigral dopaminergic neurons and formation of ubiquitin-positive aggregates in nigral neurons. We investigated the neurotoxicities of rotenone using PC12 cells. Rotenone induced PC12 cell to die in concentration dependent manner. Degenerating PC12 cells were stained by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling and anti-active caspase3 antibody, indicating that the degenerating PC12 undergo cell death via apoptosis. The endoplasmic reticulum (ER) stress were found to be involved in this rotenone-induced apoptosis because upregulation of CHOP and activation of Jun-N-terminal kinase (JNK), ER stress activated substrates, were observed. Upregulation of mRNA of BiP, an ER-specific chaperone, and splicing of the mRNA of the X box binding protein were observed, indicating the occurrence of the unfolded protein response (UPR). Prominent production of reactive oxygen species (ROS) was observed after rotenone exposure. Preincubation of resveratrol, an antioxidant polyphenol included in red wine, reduced the rotenone-induced ROS and UPR. The viability of PC12 cells was increased by resveratrol. These data suggested that resveratrol has preventive effects on PD. [J Physiol Sci. 2007;57 Suppl:S114]

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Intracellular recordings made from pyramidal neurons in the rat hippocampal CA1 region revealed that superfusion with oxygen and glucose-deprived medium (in vitro ischemia) produced a rapid depolarization after 6 min of exposure. When oxygen and glucose were reintroduced immediately after the rapid depolarization, the membrane depolarized further, reaching 0 mV (membrane dysfunction) in CA1 pyramidal neurons. To assess effects of proteoglycans on the membrane dysfunction produced by in vitro ischemia, changes in cytoplasmic Ca²⁺ concentration ([Ca²⁺]_i) from Fura-2/AM loaded slices were also measured. Pretreatment of the slices with polysaccharide lyases acting on heparan sulfate (heparinase II and III, 1 U/ml) or chondroitin sulfate (chondroitinase ABC, 20 mU/ml) did not prevent the generation of the rapid depolarization and the corresponding rapid increase in [Ca²⁺]_i in the pyramidal neurons. In contrast, the membrane was significantly restored toward the preexposure potential levels after the reintroduction. Heparinase II and III, but not chondroitinase ABC, prolonged the latencies of both the rapid depolarization and the rapid increase in [Ca²⁺]_i, and completely restored the [Ca²⁺]_i to the preexposure level after the reintroduction. These results suggest that heparan sulfate and chondroitin sulfate proteoglycan may contribute, at least partially, to the generation of the membrane dysfunction of the CA1 pyramidal neurons produced by in vitro ischemia. [J Physiol Sci. 2007;57 Suppl:S114]

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