Although electrical properties of the dendrites are going to be clarifying, little is known about the physiological roles of dendritic spike. Since spike backpropagation could depolarize the inhibitory postsynapses, it may induce transient suppression of GABAergic inhibition (DSI) through an activation of presynaptic cannabinoid receptor (CBR). In this study, we examined whether action potentials induce DSI in mouse hippocampal neurons. Whole-cell voltage-clamp or current-clamp recording was made from the soma and/or the dendrite of CA1 neurons, and changes in amplitude of IPSCs (or IPSPs) after antidromic action potentials were analyzed. We found that train of antidromic spikes could induce transient suppression of GABAergic IPSCs (or IPSPs), which have CBR-dependent and TEA-sensitive components. However, depolarization by current injection to the dendrite failed to induce CBR-dependent suppression, indicating that somatic depolarization was required. In the presence of TEA, application of phorbol ester, which facilitates spike backpropagation, enhanced DSI, and application of somatostatine, which inhibits backpropagation, reduced DSI. These results suggest that in physiological condition antidromic invasion of Na⁺ spikes into dendrites induce DSI in hippocampal GABAergic synapses. Supported by a grant from Japanese Ministry of Education, Science, Sports and Culture (to H.T). [J Physiol Sci. 2007;57 Suppl:S153]

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Prostaglandin (PG) D₂ produced in CNS regulates sleep, body temperature and nociception. Although mRNAs of PGD₂ receptors were expressed in hippocampus, little is known about how PGD₂ affect electrical activities of neurons. In this study, we examined effect of PGD₂ application on excitatory synaptic transmission in hippocampal neurons. Whole-cell voltage-clamp recording was made from CA1 pyramidal neurons in slice obtained from mouse hippocampus. Electrical stimulation was delivered to the Shaffer collateral/commissural fibers through a bipolar tungsten electrode with 5 sec intervals, and excitatory postsynaptic currents (EPSCs) were continuously recorded. Main composition of the pipette solution was potassium gluconate, and holding potential was around -70 mV to minimize a contamination of GABA-A receptor mediated IPSC. After puff application of PGD₂ (–0.5 μM) variance of EPSC amplitude increased although mean amplitude of EPSCs did not significantly change. Increase in EPSC variance was also observed by application of PGD₂ receptor agonist, BW245C. Further results showing that application of PGD₂ inhibited depolarization-induced Ca²⁺ transient, and that change in EPSC variance was not detected in the neurons pretreated with tapsigergin support a view that the PGD₂-induced modulation of EPSCs was responsible for deficiency in intracellular Ca²⁺ mobilization in pre- and/or post-synaptic sites. [J Physiol Sci. 2007;57 Suppl:S153]

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The synaptic transmission at hippocampal mossy fiber (MF) synapses is modulated by protein kinase C (PKC) at the presynaptic terminal. The mechanisms of this modulation were investigated at individual MF terminals. We used a TV-42 transgenic mouse line that expresses synaptopHluorin (SpH), one of optical probes measuring exo-endocytosis, specifically in the hippocampal mossy fiber terminals. The mouse was deeply ether-anesthetized and the brain was removed. The hippocampal slices were made at 400 μm. Individual large mossy fiber terminals were identified under confocal microscopy and the activity-dependent changes of SpH fluorescence were measured. The activity-dependent change of SpH fluorescence was on average increase by phorbol esters, synthetic analogues of diacylglycerol, whereas not by 4α-phorbol, one of inactive analogues. Phorbol esters increased the fusion probability of a vesicle in some boutons (type 1), whereas they preferentially increase the readily releasable pool in others (type 2). Some other synapses are presynaptically silent but become releasable upon exposure to phorbol esters (type 3). These effects were almost completely inhibited by staurosporine, one of PKC antagonists. Thus the PKC-dependent exocytosis modulation is variable from MF synapse to synapse. All animal procedures were conducted in accordance with the guiding principles of Physiological Society of Japan. [J Physiol Sci. 2007;57 Suppl:S154]

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In the central nerves system (CNS) synapses long- and short-term modification of synaptic vesicle exocytosis is one of basic mechanisms underlying learning and memory. Synaptic vesicles recycle through the elementary processes as docking, priming, fusion and endocytosis. The dynamics of these processes are physiologically quantified by two parameters; the readily releasable pool (RRP) which is assumed to be the number of docked/primed vesicles to plasma membrane and the fusion probability of a vesicle to plasma membrane. Here, we report the vesicular dynamics of a single mossy fiber presynaptic terminal in the acute slice of mouse hippocampus. We used a TV-42 transgenic mouse line that expresses synaptopHluorin, one of optical probes measuring exo-endocytosis, specifically in the hippocampal mossy fiber terminals. The mouse was deeply ether-anesthetized and the brain was removed. The hippocampal slices were made at 400 μm. Individual large mossy fiber terminals were identified under confocal microscopy and the activity-dependent changes of synaptopHluorin fluorescence were measured. The fusion probability of a vesicle was 0.02 on average whereas the RRP was large. It is suggested that the small fusion probability enables the stable neurotransmission during high frequency activity or potentiation. All animal procedures were conducted in accordance with the guiding principles of Physiological Society of Japan. [J Physiol Sci. 2007;57 Suppl:S154]

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Recent experiments indicate that LTP in afferent inputs to the lateral nucleus of the amygdala serves an essential function in the process of fear conditioning, model of associative learning. It remains unclear, however, how the information that is contained in the specific afferent input activity is preserved during fear learning. To address this issue, we recorded activity in two independent inputs implicated in auditory fear conditioning, a direct pathway from the auditory thalamus and indirect from the auditory cortex, which converge on the same neuron. Pairing of presynaptic stimulation of either cortical or thalamic input with action potential evoked in a postsynaptic cell by depolarizing current injections through the recording electrode led to LTP in either pathway, when GABA A receptors were blocked. With GABA A receptor-mediated inhibition present, the EPSP-spike induction protocol failed to induce LTP in the thalamic pathway, while LTP in the cortical pathway was diminished but still could be observed. The analysis of input-output curves for both monosynaptic EPSP and disynaptic IPSP recorded in convergent inputs revealed that feedforward inhibition is enhanced in thalamic pathway when compared to cortical input. The stronger inhibitory drive in thalamic pathway decreases activation of NMDA receptors and thus affects the induction of LTP at thalamo-amygdala synapses. These results suggest that the differential inhibitory control of synaptic transmission at convergent inputs may contribute to spatial specificity of LTP in fear conditioning pathways. [J Physiol Sci. 2007;57 Suppl:S154]

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The organization of phosphorylated extracellular signal-regulated kinase-like immunoreactive cells (pERK-LI cells) in the trigeminal spinal nucleus and the upper cervical cord were studied following capsaicin stimulation of the orofacial regions in rats. Rats were perfused 5 minutes after capsaicin injection and sections from the medulla and upper cervical cord were processed with pERK immunohistochemistry. A large number of pERK-LI cells were expressed in the rostro-caudally middle portion of ipsilateral the trigeminal spinal nucleus interpolaris and caudalis transition zone (Vi/Vc zone) after capsaicin injection into the vibrissal pad and snout. On the other hand, those were restricted in the ventrolateral portion of the Vc/C2 zone following orbital injection. Following capsaicin injection into the tongue, lower or upper lip, pERK-LI cells were expressed in the dorsomedial portion of the ipsilateral Vi/Vc and Vc/C2 zone. The present findings suggest that the face nociceptive information was processed in the trigeminal nociceptive neurons restricted in the Vi/Vc zone, whereas those from the intra-oral structures were processed in nociceptive neurons distributed in wide area of the Vi/Vc and Vc/C2 zones through activation of the MAP kinase intracellular signal transduction pathway. [J Physiol Sci. 2007;57 Suppl:S154]

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The escape behavior, phosphorylation of ERK in the trigeminal spinal nucleus caudalis (Vc) and Vc neuronal activity to noxious and non-noxious stimulation of the face were precisely analyzed in the rats with the chronic constriction nerve injury (CCI) of the infraorbital nerve (ION). The thresholds for escape from mechanical stimulation applied to the whisker pad area ipsilateral to the ION-CCI were significantly lower than that for the contralateral whisker pad more than 14 days after the ION-CCI. A large number of pERK-LI cells were expressed in the Vc 7 days after ION-CCI. The pERK-LI cells were restricted in the superficial laminae of the caudal Vc following mechanical stimulation of the whisker pad region. The number of pERK-LI cells was increased following increase in the mechanical stimulus intensity. Twenty one WDR neurons were recorded from Vc and response properties of these neurons were precisely analyzed. The afterdischarges of WDR neurons on the ipsilateral side relative to the CCI were significantly larger at 7 days after the operation than that of naive rats. Noxious evoked responses of WDR neurons were significantly enhanced at 7 days after ION-CCI. The evoked responses to 50 degree C heat stimulation of the face were significantly higher than naive rats. The present findings suggest that an activation of the intracellular MAP kinase cascade reflects the enhancement of the Vc neuronal excitability following ION-CCI and play an important role in the development of the mechano-allodynia induced by the trigeminal nerve injury. [J Physiol Sci. 2007;57 Suppl:S155]

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The susceptibility of synaptic transmission to the stimulation frequency is a characteristic feature of immature animals, and has been attributed to the incompleteness of transmitter release mechanisms. In an isolated spinal cord preparation of newborn rat, monosynaptic reflexes (MSRs) evoked by dorsal root stimulation, were mediated by both NMDA and non-NMDA glutamate receptors. In normal conditions, MSRs were constant in amplitude at 1/15sec, and were completely eliminated by CNQX, which suggested normal MSRs were apparently dependent on non-NMDA glutamate receptor. When stimulus rate was increased to 1/sec, MSR amplitudes were greatly reduced initially, and recovered later. This recovery of MSR was eliminated by APV. In the presence of APV, (non-NMDA component of) MSRs were depressed and not recovered at 1/sec. This non-NMDA component of MSRs appeared in constant amplitudes in the presence of cyclothiazide at 1/sec. In the presence of CNQX and 0-Mg, (NMDA component of) MSRs were depressed initially and recovered at 1/sec. From these results, non-NMDA glutamate receptor mediated almost all of MSRs at 1/15sec in normal conditions, but not at 1/sec due to desensitization. In contrast, NMDA glutamate receptor does not mediate normal MSRs at 1/15sec, but activated at 1/sec in place of non-NMDA receptor. In conclusion, incompleteness of transmitter release mechanisms could not be solely attributed to the immature feature of synaptic transmission, that is, the susceptibility to the stimulation frequency. [J Physiol Sci. 2007;57 Suppl:S155]

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Development and function of neural cells are known to be highly sensitive to structural geometry of scaffold; however, the cellular kinetics depending on the structural geometry is not fully elucidated. Recently, we have established the technique for fabricating microstructurally patterned polystyrene thin films that can be used for microscopic observation even with objectives of high power. Using the patterned films as scaffold, we quantitatively evaluated the effects of microstructural patterns on the morphology and cellular function of NGF-treated PC12 cells, and clarified the mechanisms. GFP imaging revealed that neurite growth of PC12 was strongly influenced by microstructural patterns: the neurite number per cell decreased while the length of a neurite increased. In addition, cell function evaluated using Ca²⁺ sensitive dye (Fluo4) was greatly affected by microstructural patterns: cellular excitability induced by concurrent electrical filed stimulation was enhanced when compared with the cells on a non-patterned film. However, with regards to cellular excitability to a single cell soma stimulation, no significant effect due to the microstructures was observed. These results indicate that the microstructures are actually behaving as a barrier that causes confined neurite extension, and the enhanced cellular excitability seems to be caused by the modification of electrical environment due to the existence of microstructure rather than the modification of electrical properties of a single cell level. [J Physiol Sci. 2007;57 Suppl:S155]

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At individual glutamatergic synapses, the amount of released glutamate per action potential determines the synaptic strength. However, the direct measurement of synaptically released glutamate has not been done. To measure glutamate release at single synapses, we developed a novel fluorescent glutamate probe called EOS (Glutamate Optical Sensor). Electrically evoked glutamate release was successfully detected at synapses in cultured hippocampal neurons. We found that released glutamate varied in amount among synapses. Also, we found that changes in release probability by manipulating extracellular calcium concentration were associated with changes in the amount of released glutamate at individual synapses. These findings suggest that single synapses contain several release sites. In the presence of tetrodotoxin, we detected spontaneous glutamate release which was stochastic and variable in amplitude. Further, the frequency of spontaneous release was increased upon application of high concentrations of sucrose. These properties were similar to those of miniature EPSC. Surprisingly, spontaneous glutamate release often occurred at non-synaptic sites. Moreover, the amount of spontaneously released glutamate had a tendency to be larger than evoked one. In summary, we evaluated the functional release properties of each individual synapses by using EOS. [J Physiol Sci. 2007;57 Suppl:S155]

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Homer is an adaptor protein that exists in postsynapse and modulates the physiological functions of various proteins in neuron. Recently, it has been shown to be involved in some pathological conditions of brain, so that clinical significances of Homer tend to be increased.Our group has cloned Homer2 as one of the developmentally regulated gene in mouse cerebellum and clarified its basic features in mouse brain and some interesting roles at synapses. This time, we studied molecular mechanisms of Homer in neuronal apoptosis and ischemia.In biochemical and physiological studies of cerebellar granule cells, it was clarified that Homer modified the functions of NMDAR. While short form Homer is known to be an immediately early gene and work as a dominant negative form, it prevented apoptosis in cell level. These results indicated that Homer should adjust Ca²⁺ toxicity through NMDAR. Next, we investigated the molecular dynamics of Homer in brain ischemia, one of the most important diseases related to the neuronal apoptosis. In oxygen-glucose deprivation of hippocampal neurons, intrinsic cell protective mechanisms worked after ischemia, such as attenuation of interactions between Homer and other proteins, morphological changes of spines and so on. On the other hand, in the mouse brain ischemia model by occlusion of carotid arteries, the amounts of postsynaptic proteins were increased after reperfusion and enhancement of interactions between Homer and other proteins were observed. From these results, it is suggested that malfunctions of intrinsic cell protective mechanisms should become symptomatic exacerbating factors after brain ischemia. [J Physiol Sci. 2007;57 Suppl:S156]

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Enkephalinergic neurons have been found in several areas of the central nervous system (CNS), including the spinal cord. In the spinal cord, neurons containing enkephalin exist mainly in the superficial laminae of the dorsal horn, and play an important role in the transmission and modulation of nociceptive information. To investigate the functional roles of enkephalinergic neurons in the CNS, we attempted to visualize enkephalinergic neurons in vivo. We first generated Bacterial Artificial Chromosome (BAC) transgenic mouse, in which enhanced green fluorescent protein (EGFP) is expressed in enkephalinergic neurons under the control of the preproenkephalin gene (penk) promoter. A BAC-penk-EGFP transgenic vector that has inserted EGFP in a penk gene locus was constructed by using a BAC recombination system (λ-Red recombination system). Immunohistochemical studies indicated that in the CNS, the expression pattern of EGFP is similar to that of endogenous enkephalin. This transgenic mouse allowed us to identify enkephalinergic neurons in vivo. [J Physiol Sci. 2007;57 Suppl:S156]

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Organotypic cultures of the spinal cord were obtained from mouse embryos at days 14-15 of gestation, following two different protocols. In one protocol, the spinal cord was cut into 150 μm thick transverse sections. Slices were transferred onto collagen-coated coverslips that were then placed within culture dishes. Cultures were maintained in a humidified incubator under an atmosphere containing 5% CO₂. In the other protocol, the spinal cord was chopped into 0.4 mm slices that were embedded in plasma clot on cleaned glass coverslips. The coverslips were introduced into conical plastic tubes on the drum of a tube roller, incubated in a dray atmosphere.From 1–14 days in vitro, tight-seal whole-cell recordings were made from neurons located in the superficial dorsal horn and in the deep dorsal horn. The recordings were also made from presumable motor neurons located in the ventral horn. In the presence of tetrodotoxin, the spontaneous miniature postsynaptic currents (mPSCs) were recorded at a holding potential of -70mV. These mPSCs were identified as mEPSCs mediated by NMDA and non-NMDA subtype of glutamate receptors, and mIPSCs mediated by either glycine or GABA_A receptors.The organotypic slice culture of spinal cord may provide an opportunity to investigate synaptic transmission and neuronal properties in the spinal cord. Further pharmacological characterization of neurons in organotypic slice culture of the spinal cord would clues for understanding of development and differentiation in the spinal cord. [J Physiol Sci. 2007;57 Suppl:S156]

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Hippocampal slices were obtained from C3H/HeN mice of 22-week-old (4 estrus/ 5 metestrus/ 6 diestrus females, and 5 males). After stimulating the molecular layer of the dentate gyrus (DG) by single square-wave pulse with intensities increased stepwisely from 10 to 900 μA, field potentials were recorded from the molecular layer and the granule cell (GC) layer simultaneously. The input-output (I-O) relationship of the field excitatory postsynaptic potential (fEPSP) was compared among the three phases of estrous cycle. In the case of stimulation with lower current (10–100 μA), the fEPSP slopes measured in the GC layer showed similar patterns across the phases whereas those in the molecular layer showed different patterns between estrus and non-estrus phases; in the slice from non-estrus mice the I-O curve of slope did not show a simple sigmoid form but a delayed rise or a decrease into negative value. Moreover, pattern of the increase in male mice resembles that in estrus mice. This variation across estrous phases may be due to a sex hormone-dependent change of excitability of interneurons that extend axonal fibers within DG molecular layer, such as molecular layer perforant path-associated cells (MOPP cells). [J Physiol Sci. 2007;57 Suppl:S156]

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It is demonstrated in cats and monkeys that disynaptic pyramidal excitation in forelimb motoneurons can be mediated via propriospinal neurons (PNs) located in the C3-C4 segments. In contrast, it is still under debate whether there are indirect corticosmotoneuronal (CM) excitatory projections to forelimb motoneurons in humans. In the current study, we reassessed the pathways in humans, using peri-stimulus time histogram (PSTH) technique of single motor unit (MU) firing probability following stimulation of the pyramidal tract. In 9 subjects, who all gave informed consent, activities of a MU were recorded from the biceps brachii (BB) or the first dorsal interosseous (FDI) muscle during weak cocontraction of the muscles. Pyramidal stimulation was achieved by transcranial magnetic or electrical stimulation (TMS or TES) of the contralateral primary motor cortex, or electrical or magnetic cervicomedullary stimulation (CMS). PSTHs were constructed with a bin width of 0.1 ms. TMS produced multiple peaks at short latencies in the PSTH of BB (50/57 MUs), whose total duration (4.5+2.0 ms) was longer than the corresponding value of FDI. TES or CMS could also produce multiple peaks in BB (31/60 MUs; mean duration: 1.9+1.2 ms). We conclude that stimulation of the pyramidal tract could activate indirect CM inputs also in humans, especially in an arm muscle. Results of CMS suggest that the inputs are partly mediated by spinal neurons, including PNs. [J Physiol Sci. 2007;57 Suppl:S157]

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Our monkeys learned to pick up forceps for food-taking: when food was in left and forceps in right of them with its tip facing food ( 3 o.clock), monkeys reached for and grasped forceps using right hand and brought it to and picked up food. We showed that they can invent strategies to use forceps. Here, we studied further in two monkeys what they had learned from the 3 o.clock task and how they learn new motor tasks when the learned task is modified. First, we presented forceps with the tip directed opposite (9 o.clock) from original. At the first trial on the 9 o.clock task, both did not take action at the beginning, and when prompted, one monkey refused and the other reluctantly reached (i.e. taking a longer time before reaching) and grasped forceps backward. The latter refused to act after ca 20 trials. Second, the direction of forceps was changed by a step of 30 deg from 3 to 9 o.clock. In 4-5 days, they became to grasp forceps correctly on 9 o.clock task by taking two motor steps: they first reoriented forceps and then grasped it in order. The strategies may have emerged during practice: e.g. they sometimes changed the grip when they grasped forceps too short or too long, or when he grasped it reversely, they shifted forceps to the left hand and then return it to the right hand to correct the direction. We suggest that initially they soon understood that the 9 o.clock task was a novel one for which they had no motor program, and that they solved the new tasks by recalling appropriate motor memories stored through active practice in the past. [J Physiol Sci. 2007;57 Suppl:S157]

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In order to investigate effects of physical exercise on cognitive functions in monkeys, an isokinetic machine for testing and training a monkey (monkey version of StrengthErgo240) was developed. Two monkeys were trained for 4-7 months with the machine (exercise group), and consumed energy was then recorded with rotary numbers. The two monkeys were trained to move hand at self-pace (self-paced hand movement) before the physical exercise. The 5 monkeys as control (no-exercise group) were trained for self-paced and audio-initiated hand movements, in which cortical field potentials were recorded with reaction times from stimulus onset to movement start. While the two monkeys learned audio-initiated hand movements after the exercise, reaction times were recorded. The analyzed results were compared with those in the no-exercise group. It was found that the monkeys in the exercise group learned audio- initiated hand movements significantly in shorter time than those in the no-exercise group. Cortical field potentials were also recorded by electrodes implanted on the surface and at a 2.0-3.0 mm depth in the prefrontal and motor cortices in one monkey in the exercise group during learning processes of audio-initiated hand movements, and compared with those in the no-exercise group. Plastic changes in cortical field potentials related to recognition and skill learning of audio-initiated hand movements were found to develop in very shorter time in the exercise group than those in the non-exercise group. This suggests that physical exercise elevated cognitive functions in monkeys. [J Physiol Sci. 2007;57 Suppl:S157]

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To examine functional roles of primary motor cortex (M1) in the control of primate locomotion, we recorded activity of M1 neurons during quadrupedal locomotion in a freely-moving monkey using a custom-made electromotive micromanipulator. To date, 20 neurons recorded in M1 trunk/hindlimb region were analyzed. During locomotion, almost all neurons (19/20) exhibited task-related modulation. Of these, 18 neurons modulated their discharge phasically time-locked to the step cycle and the rest modulated tonically. Mean firing frequency of task-related neurons during locomotion (15.6±1.7 spikes/s) was higher than that during standing (5.6±1.5 spikes/s). For neurons showing phasic modulation, the peak activity occurred at widely different times during the step cycle in different cells. Thirteen cells peaked once (mono-phasic) and 5 peaked twice per step (bi-phasic). Frequency of the peak activity ranged from 16.2 to 98.4 spikes/s (mean 40.2±4.6 spikes/s). Of the task-related neurons, 8 were tested for the effects of treadmill speed on their discharge patterns and all increased their discharge frequency as the speed increased. Four out of them clearly showed linear relationship between mean and/or peak discharge frequency and the speed. All these results suggest the possibility that output from M1 in macaque monkeys directly and/or indirectly acts on spinal circuitries generating a basic pattern of rhythmic activity during simple locomotion in a manner different from that in subprimates. [J Physiol Sci. 2007;57 Suppl:S158]

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Transcranial magnetic stimulation (TMS) can change the size of the H-reflex. An important feature of pulsed magnetic stimulation is the direction in which the induced eddy current flows within the target tissue. The purpose of the present study was to clarify the relationship between the direction of eddy current and the modulation of H-reflex in rats. Rats were anesthetized with ketamine, and TMS was applied using a figure-eight coil. In motor evoked potentials (MEPs), the direction of the eddy current was defined as 0 degree at midline from caudal to the rostral sides and 90 degrees at the line between both ears. The coil was rotated in clockwise and counterclockwise directions, so that it was oriented right (R) and left (L) at 0-90 degrees. In H-reflex, a silver bipolar electrode was used for sciatic nerve stimulation. Compound muscle action potentials were recorded using copper wire electrodes implanted surgically into the tibialis anterior muscle. The effects of TMS on the H-reflex were studied with a conditioning-test paradigm and various interstimulus intervals (ISIs). The H-reflex was conditioned by TMS at ISIs ranging from 2 to 10 ms. The effects of conditioning TMS on the test H-reflex differed according to the intensity of the magnetic stimuli and the direction of eddy current. The conditioned H-reflex decreased significantly but at ISIs from 5 to 8 ms remained unchange when eddy current was perpendicular to the midline of the brain (L90 and R90). Our finds suggest that the changes in the TMS-conditioned H-reflex reflect modulating excitability in the spinal motoneuronal population. [J Physiol Sci. 2007;57 Suppl:S158]

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The prepositus hypoglossi nucleus (PHN) is an important center of the brainstem circuitry involved in controlling horizontal eye movements. Previously, we classified PHN neurons on the basis of three membrane properties: afterhyperpolarization (AHP), firing patterns, and responses to hyperpolarizing current pulses. To further clarify functional significances of the classified PHN neurons, information about neurotransmitters contained in each neuron is needed. In the present study, we investigated the relationship between membrane properties and expression patterns of cellular markers for excitatory and inhibitory neurons using the whole-cell patch clamp technique combined with reverse transcription-polymerase chain reaction (RT-PCR) analysis in rat brainstem slices. From the single-cell RT-PCR analysis, we identified PHN neurons as either glutamatergic (n = 19) or GABAergic neurons (n = 43), although a small number of cholinergic (n = 2) and glycinergic neurons (n = 1) were identified. Both glutamatergic and GABAergic neurons showed a wide variety of membrane properties; however, we found that several membrane properties such as 1) single-component AHP, 2) firing pattern of a delay in the generation of the 1st spike, and 3) firing pattern of the 1st interspike interval (ISI) longer than the 2nd ISI were preferential properties of GABAergic neurons. These preferential membrane properties are useful for identifying GABAergic PHN neurons. [J Physiol Sci. 2007;57 Suppl:S158]

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This study aimed to investigate characteristics of interlimb coordination in quadrupedal locomotion of decerebrate rabbits. Under halothane anesthesia, rabbits (NZW, 2-3 kg) were decerebrated at the precollicular-postmammillary level. The head was then fixed in a stereotaxic apparatus, and the body was supported by rubber belts. To evoke locomotion, 50-Hz stimuli (10-110 μA, 0.2 ms duration, 5-10 sec) were applied to the midbrain cuneiform nucleus (CNF) with Wood's-metal-filled glass microelectrodes. Extensor and flexor EMG activities of the four limbs were recorded during locomotion and their phase relationships were investigated. When the CNF was stimulated, left and right hindlimbs consistently exhibited in phase movements, but bilateral forelimbs basically displayed left-right alternating movements. Despite such differences, the forelimb movements were synchronized with the hindlimb ones. The phase differences of left vs. right forelimbs were usually circa 180° (viz. in opposite phase), but during strong CNF stimulation in some cases, they shifted from 180° to e.g. circa 230°. In contrast, after spinal cord transection at the thoracic level, left and right forelimbs displayed in opposite phase movements at any stimulus intensity. These findings suggest that activities of the central pattern generators (CPGs) for forelimb locomotion are largely influenced by those of hindlimb CPGs. Functional couplings of fore- and hindlimb CPGs would be essential for elaborating synergistic quadrupedal locomotion. [J Physiol Sci. 2007;57 Suppl:S158]

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While it has been accepted that midbrain or thalamic animals can exhibit the righting reflexes except the visually evoked one (Magnus, 1924), little is known about functional roles of midbrain structures on the righting reflexes. To understand their functions, partial lesions were given to the medial part of the midbrain tegmentum, and effects on air righting movements were examined. Under deep anesthesia, surgical or electrolytic lesions were made in Wistar male adult rats. Air righting movements were video recorded post operative days (p.o.d.) 2-3 and 7-8 and analyzed frame by frame. In animals with the midbrain lesioned, while air righting were sometimes abolished p.o.d.2-3, it was recovered p.o.d.7-8, but the onset time of the righting after falling was remarkably longer than intact animals. Furthermore, various defects were noted; insufficient body turns around the longitudinal axis, yawing around the falling axis, and head-up or head-down rotation around the pitching axis were often observed. The medial part of the midbrain was assumed to play important roles in control of the air righting reflex according to the initial falling condition. [J Physiol Sci. 2007;57 Suppl:S159]

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To show the functional differences between mono- and bi-articular muscles, we recorded EMG activties of m. deltoideus and m. tricepus bracjii caput lateralis (mono-articular) and m. triceps brachii caput longum (bi-articular) during multidirectional targeting movements of a bipedal animal (human) and four-legged animal (cat). The results revealed distinct differences between the activation patterns of mono- and bi-articular muscles in human and cat. The bi-articular muscle is the majour muscle activated during targeting movements in various directions, and show large amplitude EMG bursts with long duration and short latency. Activation of the mono-articular muscles was strongly affected by movement direction, whereas that of bi-articular muscles was not. The EMG burst characteristics in cat were bilateral, which differed from the findings in human. [J Physiol Sci. 2007;57 Suppl:S159]

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To investigate motor cortical inputs to the subthalamic nucleus (STN), we examined the responses of the STN neurons to the stimulation of the primary motor cortex (M1) and the supplementary motor area (SMA). Stimulating electrodes were chronically implanted in the orofacial, forelimb and hindlimb regions of the M1 and the forelimb and hindlimb regions of the SMA in a Taiwan macaque (Macaca cyclopis). Among 144 STN neurons with cortical inputs, about 40% neurons responded to both M1 and SMA stimulation, and most of them responded to the stimulation of multiple body parts. On the other hand, other 60% neurons responded exclusively to either M1 or SMA stimulation, and most of them responded to the stimulation of a single body part. Neurons responding mainly to the M1 stimulation were distributed in the dorsolateral part of the STN, while neurons responding mainly to the SMA stimulation were found mainly in the ventromedial part. In the M1 domain of the STN, neurons responding to the stimulation of the orofacial, forelimb and hindlimb regions were represented in its lateralmost, central and medial parts, respectively. In the SMA domain, neurons receiving inputs from the forelimb region were located more medially than those receiving inputs from the hindlimb region. These somatotopical arrangements agree well with previous anatomical studies (Nambu et al., 1996). The present study clearly showed that cortical inputs from the M1 and SMA to the STN are somatotopically organized in spite of considerable convergent inputs from these cortical areas. [J Physiol Sci. 2007;57 Suppl:S159]

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In this study, intraspinal axonal trajectories of corticospinal tract (CST) neurons in the digit area of the monkey motor cortex were quantitatively analyzed. In two adult rhesus monkeys, biotinylated dextran amine was injected into the digit area of the motor cortex, which was identified by intracortical microstimulation technique. Among the stained CST axons, those in the lateral funiculus contralateral to injection occupied 93 ± 6% (statistics in 54 slices from the 2 monkeys) in the C2-Th2 segments, and those on the ipsilateral side comprised 4.2 ± 4.0%. The CST axons descending in the ipsilateral ventral funiculus comprised 2.8 ± 2.6%, whereas no CST axons were found in the ventral funiculus on the contralateral side. No CST axon was found in the dorsal column on either side. The CST axons on the contralateral side to injection were mainly terminated in Rexed lamia VII of all the segments, and lamina IX in cervical enlargement (C6-Th1). On the ipsilateral side to injection, CST axons were mainly terminated in lamia VII of the C1-C4 segments and in lamina VIII of the C6-C8 segments, respectively. CST axons crossing the midline, were found mainly in the cervical enlargement. Furthermore, the crossed axons originating from bilateral CST axons terminated in laminae VII-IX after crossing the midline. These results clarified a novel aspect of ipsilateral corticospinal control of spinal circuits. [J Physiol Sci. 2007;57 Suppl:S159]

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The motor cortex outputs neural commands to recruit motor units (MUs) according to the intended movement. Only a few previous studies have succeeded in recording the cortical potentials related to the MU recruitment (Kato and Tanji, 1972; Kristeva and Kornhuber, 1980). However, because these studies examined a cortical potential related to only the MU having the lowest recruitment threshold force (RTF) values recruited at the movement onset, it seems likely that these potentials included not only the cortical activity for MU recruitment, but also that for intended movement. Therefore, we attempt to record the cortical potentials involved in the recruitment motor units during gradual force exertion isolating movement onset. Subjects were asked to exert isometric contraction increasing the force gradually and slowly (Ramp contraction) by their index finger. More than two MUs had different RTF values were recorded from the first dorsal interosseous muscle concurrently. The EEG was averaged with respect to the first spike of discharges in each MUs. We observed the two cortical potentials. First, we observed negative slope before the movement, but it seemed to be the readiness potential rather than the activity for MU recruitment. Second, sharp negative deflection appeared after the first spike of several MU discharges.We confirmed cortical potentials related to recruiting single MUs under recruitment progressing isolating movement onset. [J Physiol Sci. 2007;57 Suppl:S160]

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Muscle spindle sensitivity is altered by specific types of earlier conditioning of the muscle due to a muscle property known as intrafusal muscle thixotropy. Short-length contraction (hold-short conditioning) of a muscle leads to increases in muscle spindle sensitivity of the muscle to stretch, whereas long-length contraction (hold-long conditioning) leads to decreases in the sensitivity. We studied the after-effect of hold-short or hold-long conditioning of the right biceps on tonic vibration reflex (TVR) of this muscle in 21 healthy men. An electrical vibrator with a frequency of 80 Hz was applied to the radial tendon of the muscle to elicit TVR. We measured the integrated surface electromyogram (EMG) to estimate the magnitude of TVR at 30, 60, 90, 120 s after conditioning. EMG values were expressed as a percentage of amplitudes from maximum voluntary contractions (MVC). EMG activity increased with vibration time increased, suggesting that the vibratory stimulus elicited TVR in the muscle. We found differences in EMG activity between conditionings. EMG activity was higher after hold-short conditioning (5.0 ± 4.7% MVC at 120 s, P = 0.001) than after its control (3.1 ± 3.5% MVC). On the other hand, EMG activity was similar after hold-long conditioning (2.4 ± 3.1% MVC) and its control (2.5 ± 2.1% MVC). In conclusion, hold-short conditioning has enhancing after-effects on TVR. [J Physiol Sci. 2007;57 Suppl:S160]

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Repetitive electrical stimulation to the cortical masticatory area (CMA) evokes rhythmic jaw movements in various species. Patterns of cortically induced rhythmic jaw movement (CIRJM) vary depending on the stimulation site. The aim of this study is to clarify the representation of pattern of CIRJMs in the unanesthetized guinea pig, in which the masticatory muscle EMG activities and the jaw movements were recorded. CIRJMs were evoked from the granular cortex lateral to the agranular cortex, which has been defined as the face MI. CIRJMs were classified into four types on the basis of jaw movement pattern: small (type A) and large (type B) vertical movement, as well as movement with large lateral shift unilaterally (type C) and bilaterally (type D). Types A and B were characterized by small amplitude of masseter activities, not similar to typical jaw movements of mastication. Types C and D were characterized by large activities in the unilateral and bilateral masseter muscle, respectively. Type C was similar to the unilateral jaw movements during chewing in natural mastication, while type D was similar to bilateral jaw movements. Types A and B were evoked from the focal area in the CMA medial to the area inducing types C and D. These results suggest that the CMA of the guinea pig may be divided into two parts with different function. [J Physiol Sci. 2007;57 Suppl:S160]

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Distribution of cortico-muscular coherence was investigated between local field potential of primary motor (M1) cortex with distal and proximal forearm representations and EMG of various forearm muscles in a macaque monkey during performance of the precision grip task. Muscle field of the recording sites in M1 was assessed by the stimulus triggered averaging of the EMG activities with the stimulus intensity below 40 μA with single pulses. We have found that M1 sites that have muscle field in the distal muscles showed clear task-related β band coherent activity (15–30 Hz) with EMG of the distal muscles. However, the sites that have muscle fields in proximal muscles showed no coherence with proximal muscles, but showed clear coherence with distal muscles. Even if we increased the stimulus intensity up to 40 μA and applied repetitive stimulus (20 pulses at 333 Hz), no post-stimulus effect could be observed in distal muscles from these sites. We conclude that task-related β coherent activity in M1 areas of both distal and proximal muscle representation may engage networks of neurons controlling the distal muscles. [J Physiol Sci. 2007;57 Suppl:S160]

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There are neuromusclular and perceptual constraints in the coordinated movements of the limbs. The movement of a limb therefore can be affected by that of other limbs and vice versa. In the present study, we investigated the interaction between the contraction of the hand muscle (wrist extensor) and the relaxation of the foot muscle (ankle dorsiflexor) on the ipsilateral (right) side. Subjects sat like sitting on an armchair, which enabled them to move their wrist and ankle freely, and performed five tasks: task 1) active wrist extension from a wrist flexed (relaxed) position to the horizontal position, task2) active ankle dorsiflexion from a ankle planarflexed (relaxed) position to a moderately dorsiflexed position, task3) passive plantarflexion from the moderately dorsiflexed position to the relaxed position, task 4) simultaneously doing tasks 1 and 2, and task 5) simultaneously doing tasks 1 and 3. Subjects performed each task as fast as possible and were instructed not to plantarflex actively in tasks 3 and 5. The mean and maximal wrist angle velocity, and the electromyographic activity of the wrist extensor in task 5 were smaller than those in task 1. The relaxation of the ankle dorsiflexor occurred more slowly in task 5 than that in task 3. The electromyographic activity of plantarflexors in task 5 was greater than that in task 3. It is suggested that the simultaneous hand muscle contraction and foot muscle relaxation on the ipsilateral side interfere with each other. [J Physiol Sci. 2007;57 Suppl:S161]

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The cholinergic pedunculopontine tegmental nucleus (PPTN) in the brainstem is thought to associated with reward-related behaviors by integrating polymodal signals related to the motivational state of animal, sensory information, motor control and reward. Here, we examined the effect of behavioral and reward context on neuronal activity of the pedunculopontine tegmental nucleus (PPTN) in primates during visually guided saccade tasks. About half of movement-related activities occurred for only the saccades to the saccade target in the task, but they did not occur for the saccades outside the task. On the other hand, for the other half of neurons, movement-related activities occurred for every saccade regardless of the task condition. For visual responses, some neurons responded either the initial fixation point or saccade target, and others responded equally to both stimuli. We further analyzed mutual relationship among modulation timing, preferred direction, effect of reward expectation and this context dependency of the activities, and discussed the visuo-motor processing of PPTN. [J Physiol Sci. 2007;57 Suppl:S161]

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Saccades are rapid eye movements that acquire a visual target in the fovea. Because the fovea is small, saccades must be very accurate. Saccade accuracy is ensured by a learning mechanism, called saccade adaptation, which is induced by visual error at movement end. Very little is known about central pathways that bring error signals for saccade adaptation. Here we show that microstimulation of the medial part of the midbrain tegmentum created learning signals for saccade adaptation in monkeys. Weak electrical stimuli delivered ∼200 ms after targeting saccades in one horizontal direction produced gradual and marked changes in saccade gain. The spatial and temporal characteristics of the produced changes were similar to those of adaptation induced by real visual error that was created by stepping the target during saccades. When stimulation was applied after saccades in two different directions, endpoints of these saccades gradually shifted in the same direction in two dimensions. Thus microstimulation created learning signals that dictated the direction of "adaptive" shift in movement endpoints. Our findings suggest that the error signals for saccade adaptation are conveyed in a pathway that courses in the midbrain tegmentum. [J Physiol Sci. 2007;57 Suppl:S161]

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It has been hypothesized that the superior colliculus (SC) intermediate layer lies within a gaze feedback loop and generates an error signal specifying gaze position-error, the distance between target and current gaze positions. To test coordinated eye-head movements are controlled by feedback, we briefly (less than 400 ms) stopped head motion during gaze saccades made in the dark. At the same time, we recorded fixation neurons in cat SC that fired tonically during fixation and were silent during gaze shifts. Then, descending axonal projections of the neurons were tested, using antidromic mapping technique. Stimulus currents were usually restricted to less than 50μA. Some neurons were antidromically activated from the medial part of the pontine reticular formation. Neural activity of the neurons continued steadily during a brake-induced gaze plateau with activity-level just preceding the plateau. The activity peaked near the end of the corrective saccade. We did dot find that fixation neurons with and without descending projections show different firing patterns during gaze shift perturbations, respectively. The data suggest that the fixation cells which encode gaze position-error are updated in real time and the axons project to the omnipause neuron area. [J Physiol Sci. 2007;57 Suppl:S161]

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The STN is a target for deep brain stimulation (DBS) in the treatment of Parkinson's disease. DBS effects are likely to be a mixture of multiple effects, affecting both axons and somata within the STN. We here report on experiments studying the effect of stimulation on the activity of neurons within the STN. Two monkeys received two chronic recording chambers each. The two chambers were directed at the same STN. One of them was used to carry out electrical stimulation of the STN with a microelectrode (using monophasic stimulation at 1/s, pulse width 50 μs, amplitude 50–300 μA), and the other to simultaneously record the neuronal activity in STN with standard extracellular single-unit recording techniques. Many STN neurons responded to the stimulation with a cessation of activity, starting immediately after the stimulation and lasting for 20–70 ms. The inhibition was followed by an excitation in some neurons. STN neurons remote from the stimulation site as well as those adjacent to the stimulation site ceased to fire. Prominent suppressive effects on the activity of neurons throughout the STN would result from the electrical stimulation of the STN. Given the high frequency of therapeutic DBS (130 Hz), it is unlikely that the excitatory STN output will manifest itself. The inhibitory responses may be the consequence of activation of GPe axons which then would inhibit STN neurons. [J Physiol Sci. 2007;57 Suppl:S162]

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We previously examined the effect of pedaling exercise (PE) on urinary serotonin (5-HT) level. Since we found the increase in the urinary 5-HT level after PE, we hypothesized that the activity of the 5-HT neuron located in the brain stem may increase during PE. In the present study, we investigated the effects of PE on EEG and cerebral oxygenation in prefrontal cortex (PFC) before, during and after PE. Subjects performed PE for 15 minutes. PE rate and work load were kept at 60 rpm and 90 watt. We used Fast Fourier Transform to obtain the EEG (Cz, Pz) power. Cerebral oxygenation in PFC was assessed by concentration changes in oxygenated hemoglobin (oxyHb) using multi channel near-infrared spectroscopy (NIRS). Urinary and blood 5-HT levels were measured before and after PE. As a result, we found that the spectral power of alpha band (8-13Hz) began to increase at about 7 minutes after the onset of PE. The initial decrease and subsequent increase in oxyHb level in PFC were obtained during PE. OxyHb level in PFC began to increase at about 5 minutes after the onset of PE, and reached a peak at about 13 minutes after the onset of PE. The peak level of oxyHb was higher in more ventral portion of PFC, as compared with dorsal PFC. Since the urinary and blood 5-HT levels increased after PE, we suggest that augmentation of brain 5-HT system is involved in activation of PFC and rise in alpha power of EEG during PE. [J Physiol Sci. 2007;57 Suppl:S162]

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To investigation the effect of linear head motion on dynamic visual acuity (DVA) of a high-speed moving target, we conducted two experiments. In the first experiment, fifty healthy subjects were asked to read sequentially-presented 3 random numerals moved left to right at 60 or 90 deg/s under three head conditions: 1) stationary, 2) voluntary linear movement from left to right, and 3) voluntary linear movement from right to left. In each condition, 40 trials were carried out and numbers of correct answers were evaluated as DVA score. Although the averaged DVA score in the three conditions were almost the same, we found higher DVA score in the trials in which head motion started more than 200ms prior to the onset of target motion under the condition 2). In the second experiment, nine healthy subjects were trained to start their head motion in time with an audio cue 300ms prior to the onset of target motion (80deg/s) under the condition 2). After this training, seven of nine subjects clearly improved DVA score, and their eyes moved in the same direction of head motion, which was the opposite direction of vestibuloocular reflex (VOR). This kind of eye-head motion was observed even in darkness in 3-4 trials jast after the training and diminished after 7-8 trials. The dynamic change in VOR and the contribution of predictive smooth pursuit eye movement to the visual acuity will be discussed. [J Physiol Sci. 2007;57 Suppl:S162]

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We examined whether the red nucleus (RN) lesion can modify cortically induced rhythmical jaw movements in rats anesthetized by urethane. Rhythmical jaw movements were induced by repetitive electrical stimulation of the orofacial motor cortex (OfM) and the insular cortex (IC). The RN lesions were made bilaterally by passing negative current. The distance between the maximum jaw-opening position and minimum jaw-opening positions was measured during rhythmical jaw movements. The duration of rhythmical jaw movements and the distance between the maximum jaw-opening position and minimum jaw-opening position before RN lesion was taken as 100%. The%age change in the duration of rhythmical jaw movements and the distance between the maximum jaw-opening position and minimum jaw-opening position after bilateral RN lesions were determined. The RN lesions did influence rhythmical jaw movements induced by stimulation of the OfM. The distance between the maximum jaw-opening position and minimum jaw-opening position 15 min and 30 min after lesions was significantly decreased to 60.7±15.8% and 56.1±15.9% (mean±S.E., n=10) of controls, respectively. The duration of rhythmical jaw movements 15 min and 30 min after lesions was significantly shortened to 60.4±12.6% and 42.8±12.4% of controls, respectively. On the other hand, lesions of the RN did not influence rhythmical jaw movements induced by stimulation of the IC. These results suggest that the RN is involved in the control of jaw movements induced by stimulation of the OfM. [J Physiol Sci. 2007;57 Suppl:S162]

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Activation of the medial prefrontal cortex (mPFC) is required for hyperlocomotion and expression of c-fos gene in the subthalamic nucleus (STN) in response to systemic dopamine stimulation. These reactions are mediated by dopamine D1-like and D2-like receptors in the mPFC. In the present study, we tested the possibility that the functional connectivity between the mPFC and STN may be involved in dopamine-induced motor behavior. When a retrograde tracer FluoroGold (FG) was injected into the STN, the labeled signals were observed in the mPFC pyramidal cells. Intra-mPFC injection of biotin dextran amine gave anterogradely labeled fibers innervating the STN. Systemic injection of methamphetamine (METH) elicited c-fos expression in glutamatergic projection neurons but not in GABAergic interneurons in the mPFC. Some of c-fos-positive neurons in the mPFC were retrogradely labeled by FG injection into the STN, indicating that the mPFC neurons activated by METH monosynaptically innervate the STN. These results suggest that the mPFC neurons act to facilitate dopamine-induced hyperlocomotion through the corticosubthalamic neural pathway. [J Physiol Sci. 2007;57 Suppl:S163]

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The orbitofrontal cortex (OBF) plays important role in the organization of adaptive behavior. To further characterize these functions, complex electrophysiological-neurochemical-behavioral experiments were performed in rats and rhesus monkeys. Single neuron activity was recorded in the OBF 1) during feeding or sexually motivated visual discrimination tasks, 2) microiontophoresis of neuroactive substances, i.e. glucose, catecholamines and other neurochemicals and 3) during gustatory stimulations. OBF neurons responded to various microiontophoretically administered chemicals as well as to gustatory stimulations in both species showing complex chemosensory attributes. In the monkey OBF, feeding or sexual behavior related characteristic firing rate changes were recorded. Our results indicate that OBF possesses specific endo- and exogenous chemosensitivity and it is involved in behavioral responses as well utilizing differential neurotransmitter mechanisms in integrative processes of adaptive behavior. Supported by: 21st Century COE program and Grants-in-Aid for Scientific Research (S.A.), NKTH MEDIPOLIS RET-008/2005, ETT (315/2006), National Research Fund of Hungary (T042721, M036687), and the HAS (L.L.). [J Physiol Sci. 2007;57 Suppl:S163]

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The orexins are lateral hypothalamic neurotransmitters acting in various sites of the central nervous system. The aim of the present series of experiments was to reveal whether orexin-A (OXA) in the bed nucleus of stria terminalis (BST) is involved in learning, anxiety, reinforcement and nociception. Bilateral OXA microinjections into the BST of male Wistar rats were performed in the doses of 250ng (70pmol) and 500ng (140pmol) 30 min prior to 1) open field (OPF), 2) elevated plus maze (EPM), 3) conditioned place preference (CPP), 4) passive avoidance (PAV) or 5) hot plate (HP) tests. In the EPM 500ng OXA increased the total time spent on the open arms and on the end of the open arms. Higher dose slightly increased the general motor activity in EPM and OPF. In the CPP, microinjection of lower dose increased the frequency of entering into the treatment quadrant. In the PAV, both doses decreased the retention time to enter the dark room dose-dependently. OXA did not alter pain sensation in HP. Our data show the functional heterogeneity of OXA in the BST, especially its effect on avoidance learning, which is supposed to be due to anxiolysis rather than analgesia. Supported by 21st Century COE program and Grants-in-Aid for Scientific Research (S.A.), NKTH-RET-008/2005 MEDIPOLIS, ETT 317/2006 and the HAS (L.L.). [J Physiol Sci. 2007;57 Suppl:S163]

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The purpose of this research was to examine the state of the activity of the prefrontal area during the calculation tasks in the morning and the afternoon by non-invasive the Near Infrared Spectroscopy (NIRS). The NIRS was studied for 8 volunteers (30.5±5.9 y).As a method, the near infrared rays light with a high permeability (wavelength 775, 810, 850 nm) was irradiated from the outside, and the state of the hemoglobin in blood that flowed in the tissue was measured by analyzing light that had permeated the tissue. The change of hemoglobin dynamics were sampled at 2Hz, 2ch (HAMAMATSU Corporation, NIRO-200).As the result, an increase of oxy-Hb (hemoglobin of making to oxygen) of the head was suspected for calculation tasks. And the tendency to increase was showed, when the first half of the calculation tasks was compared with the latter half. But the difference in the morning and the afternoon was not admitted.More detailed tasks to calculate will be measured by NIRS in future. [J Physiol Sci. 2007;57 Suppl:S163]

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Cerebral cortex is widely innervated by noradrenergic (NA) fibers originating from the locus coeruleus. NA is implicated in the control of behaviors, such as attention, arousal level, S/N ratio in the sensory responsiveness, and so on, but underlying mechanism to achieve such controls in synaptic level within the cortical network is largely unknown. To investigate roles of NA in the cortical network, we looked at what effects NA has on synaptic responses. Thalamocortical slices were prepared from GAD67-GFP (δneo) mice (P10-24). Excitatory postsynaptic currents (EPSCs) were recorded in voltage-clamp mode from neurons in layer IV in response to stimulations at either ventrobasal nucleus (VB) of thalamus or neighboring layer IV for activation of thalamic or horizontal inputs, respectively. EPSCs from excitatory as well as inhibitory neurons in response to VB stimulation were significantly suppressed (72% and 65% of control, p<0.05) by NA. The effect was dose-dependent. NA also suppressed horizontal inputs to inhibitory (71%, p<0.05) but not excitatory cells (p=0.24). Analyses of coefficient of variation (CV) of EPSCs suggested that NA reduced the release of transmitters acting on presynaptic terminals. These results indicated that NA largely suppresses synaptic inputs to layer IV cells with possible differential effects depending on target cell type. [J Physiol Sci. 2007;57 Suppl:S164]

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To evaluate human mind or feeling objectively, we analyzed electroencephalogram (EEG), electrocardiogram (ECG) and pneumogram. Rap music (Hip-Hop music) was applied to healthy subjects as auditory stimulus. EEG was recorded almost 30 min (5 min control, about 5 min during the music, and 15 min recovery) by Neurofax EEG-1100 (Nihonkohden, Tokyo) and analyzed by data analysis software, Focus/QP-211A. Electrode configuration of 25 points on scalp of subjects was based on the 10-10 electrode method by the International Encephalogram Federation. EEG was analyzed by mean FFT (Fast Fourier transform) to gain power of EEG spectrum and amplitudes of delta, theta, alpha (8–13 Hz), beta and gamma were calculated from the power . We detected that amplitudes of delta and theta waves on almost all electrode positions were reduced during listening the music. On the other hand, amplitudes of alpha wave were enhanced on many positions, mostly enhanced on the occipital regions, O1and O2. Amplitudes of beta and gamma waves on electrode positions, T7 and T8 in temporal and parietal regions were enhanced during the music. The amplitude of an enhancement was larger when listening more exciting stimulating Hip-Hop music. Intervals of respiratory ventilation were decreased during the music. Heart rate was markedly enhanced just after the beginning the music and sustained higher level during the music. Present results suggested that EEG, ECG and pneumogram were changed specifically in accompanying with emotional changes in response to exciting level of the subjects listening to stimulating Rap music. [J Physiol Sci. 2007;57 Suppl:S164]

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Anterior and posterior portion of the insular cortex is considered as a cortical gustatory and visceral sensory area, respectively. Many studies have indicated that both insular cortex and amygdala are important for the neural mechanisms of taste aversion learning. Anatomically, there is a reciprocal connection between the insular cortex and the amygdala. However, a few electrophysiological studies on these connections have been reported. It has been shown that GABAergic neurons have important roles in functions of the amygdala. In the present study, we investigated the changes in neuronal activity in the insular cortex after microinjection of GABA into the amygdala. Of the 9 rats, 5 were injected within or near the basolateral nucleus of the amygdala. In all 5 cases, spontaneous discharge rate of the insular cortex neurons was not affected after microinjection of GABA. In the remaining 4 rats, the injection sites were located outside of the amygdala. In these cases, spontaneous activity of the insular cortex neurons was unaffected after microinjection of GABA, except one case showing an excitatory response, which was injected into the piriform cortex. Previously, we reported that spontaneous activity of the insular cortex neurons was depressed after microinjection of glutamate into the amygdala. These results indicate that the effect of inhibitory chemical stimulation of the amygdala on the spontaneous activity of the insular cortex neurons is not simply reverse to that of excitatory chemical stimulation. [J Physiol Sci. 2007;57 Suppl:S164]

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Neural activity during memory encoding of words was investigated by means of the functional magnetic resonance imaging (fMRI). Event-related fMRI data was acquired while volunteers saw and memorized visually presented words. Recognition tests for memorized words (old words) visually displayed with new words were carried out after two different study-test delay intervals (0 h and 24 h). Volunteers had a 7 h sleep during 24 h period after encoding. Neural activity elicited by old words was classified according to whether each word was later remembered or not. Differences in neural activity elicited by old words that were later remembered and later forgotten, "subsequent memory effects", were analyzed. This procedure was applied to both study-test delays. Subsequent memory effects associated with two study-test delays were compared. Neural activity during encoding associated with later remembered words for both study-test delays was found in hippocampus and left dorsal inferior frontal gyrus. In several regions, including left ventral inferior frontal gyrus and left superior frontal gyrus, neural activity during encoding was greater for 24 h study-test delay than 0 h study-test delay. These results suggested that the neural activity in the regions exhibiting greater activations in 24 h study-test delay predicts later remembered or forgotten, and that these regions may play an important role in sleep related memory consolidation processes. [J Physiol Sci. 2007;57 Suppl:S164]

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We have demonstrated that the 10 min cycle ergometer exercise with the load as high as 60% of the maximal heart rate augmented the working memory estimated with using, either RST, or 2-back test in young people. These tests were conducted as soon as the exercise terminated. The present study was designed to know how long augmentation can be sustained after exercise. In the first, we investigated using RST if the augmented state was kept at 20 min after exercise in 14 young male volunteers. Subjects finished a 10 min ergometer exercise with loads in such a way that the heart rate attained 10, 30, or 60% of the predicted maximal heart rate. One experimental run was composed of pre-RST, exercise, 20-min rest and the post-RST. The interval between experiments was longer than one day with the order of exercise distributed equally among subjects in order to create a good balance. Mean result of RST after each exercise was compared with that before exercise with using a dually tailed t test. Only the RST after 60% exercise could induce a significant augmentation (p<0.025). Then, we have introduced RST after having 40 min post-exercise rest in 15 young student volunteers using the same protocol as in the first experiment. In this experiment, neither 15%, nor 60% exercise load induced significant increase, although probability of the t-test was decreased as low as 0.06 in the 60% exercise group. From present results, we concluded that the augmentation of working memory induced by a moderate exercise would terminate within 40 min after exercise. [J Physiol Sci. 2007;57 Suppl:S165]

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Histidyl-proline diketopiperazine (cyclo (His-Pro)), a cyclic dipeptide derived from thyrotropin-releasing hormone (TRH), is well known as neuromodulator to control food intake, but other functions are unknown. Since cyclo (His-Pro) has been found in wide areas in the central nervous system, this chemical may play roles in other physiological functions. In the present study, we investigated the effects of intraperitoneal (IP) injection of cyclo (His-Pro) at the dose of 0.1mg/kg on various behavioral tests in male Wistar rats. The effects of iontophoretically applied cyclo (His-Pro) on neuron activities in the thalamus and hippocampus were also examined using multibarrel electrodes in urethane anesthetized rats. Cyclo (His-Pro) was injected 15min before each behavioral test. In the open-field test, this chemical increased number of rearing (p <0.05) which indicate facilitating exploratory behavior. In the elevated plus maze test, cyclo (His-Pro) increased the duration of stay in closed arm (p <0.05) suggesting enhanced anxiety. In the passive avoidance test, the cyclic dipeptide reduced the retention time to move to dark compartment where a electrical shock was applied 24 h before indicating suppression of avoidance learning (p <0.05). In the electrophysiological study, cyclo (His-Pro) inhibited neural activities of hippocampal neurons. These findings suggest that the cyclic dipeptide has diverse physiological actions to regulated emotion and learning in the central nervous. [J Physiol Sci. 2007;57 Suppl:S165]

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Intermitted ingestion of sugar or fat has been shown to induce binge-type eating, a type of addictive behaviors. Highly palatable foods such as sugar or fat may affect the brain in a similar way to addictive drugs in which nucleus accumbens (NAc) is one of the major target sites. In this study, we investigated the dopamine levels in the NAc in fat binge-type eating (FBE) using in vivo microdialysis. FBE was induced by allowing rats to access to fat for 1 hour every 2nd day without any caloric restriction. In this condition, rats developed FBE and consumed approximately triple amount in 5th 1 hour fat access compared to 1st 1hour fat access. The control group had access to fat only once to avoid neophobia. After these schedules, microdialysis probes were implanted to the NAc and dopamine responses to 20 minutes fat eating were measured. In both groups, consumption of fat increased dopamine level in NAc but the response was attenuated in FBE group. The fat consumption in the 20 minutes did not differ between FBE and control group statistically and had not correlate with dopamine increase level in NAcc through both groups. The results suggest that dopamine increase in NAc does not reflect fat consumption and is less likely to be required in an expression of FBE. [J Physiol Sci. 2007;57 Suppl:S165]

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It is well known that immobilization stress for two hours decrease blood calcium levels via the gastric vagus-gastrin-histamine pathway, however, effects of other types of stress comditions and possible hypocalcemic factors are not well studies. Since neurochemical pathway to induce gastric acid secretion has been shown to share the hypocalcemic pathway, ghrelin and thyrotropin-releasing factor, peripheral and central gastric acid secreting agents are the possible candidates to induce hypocalcemia. In the present study, the effects of electrical shock (1 mA, 3 s/min 10 times), 2-buten-4-olide (2-B4O), ghrelin and TRH on blood ionized calcium levels were examined using male Wistar rats. 2-B4O is the fasting-induce anorectic agents which facilitates hypothalamo-pituitary-adrenal axis indicating a possible metabolic stress agent. Electrical shock but not psychological stress in the communication box induced hypocalcemia 15 min after initiation of stresses. Intravenous (IV) or intracerebroventricular (ICV) injection of ghrelin (0.05, 0.5, 5μg) did not affect blood calcium levels but IV and ICV injection of TRH (2, 20, 200μg) decreased blood calcium levels. 2-B4O was ineffective to induce hypocalcemia. The present study suggests that the ghrelin not take part though TRH had the possibility of taking part in the stress low calcium blood syndrome though the ghrelin and TRH were central acid in the stomach secretion promotion both factors. [J Physiol Sci. 2007;57 Suppl:S165]

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Epilepsy is a disorder of the brain characterized by repeated seizures. About 1-3% of the people in the world suffer from epilepsy. Electroencephalogran(EEG) is the most useful test in confirming a diagnosis of epilepsy. However, diagnosing epilepsy is a difficult task requiring observation of EGGs and gathering of additional information. In this study, a new approach based on continuous wavelet and artificial neural network techniques was used to analyze EEGs for epileptic rats in order to detect the specific waveform correlated with seizure occurrence automatically. We examined EEGs with the animal model for eplipsy, the Wakayama epileptic rat(WER). WER is a new mutant exhibiting both spontaneuous absence-like behavior and tonic-clonic convulsions. EEGs were recorded from the rat which was in conscious and free to move. For long-term observation, EEGs were recorded on the vibrissal somatic sensory region by a small telemetry transmitter and a receiver system. The recorded EEG waveforms were band-passed between 1.5 and 30Hz. The seizure patterns in the telemetry EEG recording were analyzed to forcus on absence-like seizure. The present study indicates that a new hybrid system comprising continuous wavelet and artificial neural network techniques might be effective for autonomic absence-like seizure detection in long-term epilepsy monitoring. [J Physiol Sci. 2007;57 Suppl:S166]

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