The immunologically induced fatigue was conducted in rats by intraperitoneal (IP) injection of a synthetic double-stranded RNAs, poly I:C. An IP injection of poly I:C (3 mg/kg) induced fever and a decrease in spontaneous activity. In vivo brain microdialysis revealed that the extracellular concentration of 5-HT in the prefrontal cortex (PFC) decreased after poly I:C injection, which was blocked by selective 5-HT reuptake inhibitor (SSRI), fluoxetine. The amount of mRNA for interferon-α (IFN-α), as well as serotonin transporter (5-HTT) mRNA, which is known to be induced by IFN-α in astrocytes, increased in the PFC. Microinjection of IFN-α decreased the 5-HT concentration, which was also blocked by SSRI. Furthermore, the poly I:C-induced suppression of activity was attenuated by 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino) tetraline (8-OH-DPAT) or SSRI. These findings, taken together, suggest that brain IFN-α and 5-HT system play an important role in the neuronal mechanisms of the immunologically induced fatigue by poly I:C.
To further investigate the central mechanisms of fatigue, we tried to make a conditioning model of immunologically induced fatigue. After habituating rats to restricted drinking (30 min a day), saccharin water was given just before the injection of polyI:C (1 mg/kg) only on the day of conditioning. When saccharin water was given again four days later, fever and reduction of spontaneous activity were observed. We further tried to investigate the central mechanisms of fatigue using this conditioned fatigue model. [Jpn J Physiol 54 Suppl:S235 (2004)]

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Tropical natives are reputed to tolerate high ambient temperatures. This results from their long-term residence in the frequently hot and often humid tropical climates. This study was designed to compare the peripheral mechanisms of thermal sweating in tropical natives to their temperate counterparts. Fifty five healthy male subjects (25 Koreans, 30.4±4.7 yr and 30 Malaysians, 28.3±4.0 yr) gave their informed written consent to be used as subjects in this study. A 10% solution of acetylcholine (ACh) was iontophoretically administered into the forearm skin. The sweat onset-time was 0.96 min shorter (P<0.01) and directly activated and axon reflex mediated total sweat output for 5 min were 1.08±0.19 mg/cm2/min and 0.42±0.11 mg/cm2/min in the temperate natives and 0.68±0.14 mg/cm2/min and 0.15±0.19 mg/cm2/min tropical natives, respectively. These values being 100% (P<0.01) and 150% (P<0.01) higher in the temperate natives compared to the tropical natives. These results indicate that suppressed thermal sweating in tropical natives is, at least in part, due to suppressed sweat glandular sensitivity to ACh through both recruitment of sweat glands and sweat output per each gland. [Jpn J Physiol 54 Suppl:S235 (2004)]

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The effects of bilateral acupuncture stimulation on the sweating in the palm and the sole were compared with the effects of unilateral stimulation previously reported. In young healthy males, right and left Zusanli acupoints were stimulated simultaneously for 20 min at 5 Hz or 100 Hz. Sweating was induced by mental arithmetic for 2 min, and sweat rate and the rate of sweat expulsion were averaged. Sweat rate was reduced by acupuncture stimulation, but the reduction was greater at 5 Hz than at 100 Hz. The reduction was observed during 30 min of the recovery as well as during the stimulation. The reduction of sweat rate was greater on the sole than on the palm when stimulated at 5 Hz. The rate of sweat expulsion was reduced by the stimulation at 5 Hz, but not at 100 Hz. At 5 Hz, the reduction was observed during 30 min of the recovery. The results confirm our previous hypothesis that the acupuncture stimulation at 5Hz affects a higher center for mental sweating to suppress the rhythm generation, whereas that at 100 Hz affects a lower center, possibly the spinal cord, to modify the efferent activity. The results indicate that the central suppression by acupuncture stimulation is prolonged by bilateral stimulation. [Jpn J Physiol 54 Suppl:S235 (2004)]

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It is known that CO₂ inhibits the activity of cold receptors and facilitates that of warm receptors of the skin. Thus, it is expected that thermal sensation was altered by CO₂ water immersion at the same water temperature compared with during fresh water immersion. We compared the effect of capsaicin and menthol applied topically to the forearm skin on temperature sensation score during the immersion of CO₂ (1000ppm) water and fresh water at 33°C for 10 min. Though slight pain occurred on the capsaicin site, temperature sensation score was ^"neutral^" before water immersion for each subject. The score shifted to the warmer sensation during CO₂ water immersion, whereas it remained ^"neutral^" or slightly shifted to the ^"warm^" during fresh water immersion. In the menthol application, a few subjects reported a ^"slightly cool^" sensation before water immersion. The score shifted to the cooler during fresh water immersion, whereas it remained ^"neutral^" or slightly shifted to the ^"warm^" during CO₂ water immersion. The change was remarkable in a later stage of the immersion. These results appear to suggest that capsaicin and menthol modify the changes in skin temperature sensation elicited by CO₂. [Jpn J Physiol 54 Suppl:S236 (2004)]

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It is well known that males sweat more compared to females, however the mechanism is still not fully understood. To elucidate the peripheral mechanisms of the gender difference in thermal sweating, sweating responses to acetylcholine (ACh), a primary transmitter of the sudomotor innervation, were compared between college-age male (n=10) and female (n=11) subjects. Ten percent ACh was iontophoretically administered on the forearm with the direct currents of 1.0, 1.5, 2.0 and 2.5 mA (Quantitative sudomotor axon reflex test). With the higher current the sweat latency tended shorter in both sex, but gender difference was not apparent. Directly activated and axon reflex-mediated sweating responses reached the maximum at a current of 1.5 or 2.0 mA in both sex, and those in the male were larger than those in the female though not significant because of the big individual variations. Iodine-pregnated paper method revealed that activated sweat gland density on the forearm in male was not lesser than in female although the expected larger forearm surface area. Sweat output per single gland was significantly large in the male than in the female. These results indicate that gender difference of thermal sweating is attributed to peripheral sweating mechanism at least in part, through both of the larger sweat output per single gland and the more number of active sweat gland on the forearm in male. [Jpn J Physiol 54 Suppl:S236 (2004)]

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Background: While acidification rate of tissues reflects global metabolism, utility of this characterization has been hampered by the need for precise and real-time measurements of a small quantity of solution. Therefore, we developed real-time pH microsensor system based on ion-sensitive field effect transistor (ISFET) which can detect pH change in less than 1 μL solution. We measured pH change and evaluate the fraction of CO₂ contribution to acidification of isolated rabbit aorta.Methods: The dimension of ISFET sensor was 0.45 mm width x 0.18 mm thickness x 5.5 mm length. Two sensors were placed at the center of isolated rabbit aorta (diameter: ~3 mm, n = 10) and one of these sensors were covered with silicon tube to assess pH change with CO₂. After 1 min continuous delivery of Tyrode solution buffered with sodium bicarbonate (pH 7.4), measurements were performed for ten min with the solution kept still at 37°C.Results: pH was decreased monotonically and saturated at ~10 min. the value of pH changes at ten min was –1.05 ± 0.42. The percentage of CO₂ contribution to the change of pH was 79.7 ± 6.1％.Conclusion: We firstly succeeded in real-time measuring acidification rate and evaluating CO₂ contribution to the change of pH of isolated rabbit aorta with ISFET based microsensor system. This technique will be useful to investigate the metabolic state of isolated tissues or cultured cells. [Jpn J Physiol 54 Suppl:S236 (2004)]

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Bitter melon is specialty food produced in Okinawa prefecture in Japan, where people enjoy notable longevity. The effect of bitter melon malt vinegar on energy metabolism was determined, and compared between normal LETO rats and genetically diabetic OLETF rats. Administration of a diet containing bitter melon malt vinegar increased daily food intake and daily energy expenditure in both strains. In LETO rats, the respiratory quotient (RQ) was decreased and the fat-derived energy used for combustion was increased by bitter melon malt vinegar. In diabetic OLETF rats, the profile of daily energy expenditure was normalized; two peaks in the daily profile of energy expenditure, which were disappeared in OLETF rats on the control diet at 24 weeks of age, were reproduced by administration of bitter melon malt vinegar. As a consequence of blood or plasma inspection, it turned out that there was no change in HbA1c but a significant increase in plasma cholesterol in the vinegar diet-fed OLETF rats. From these results, a long-term administration of bitter melon-malt vinegar can be expected to suppress a lowering of energy turnover inherent with aging and thereby improve anorexia rather than to bring about a preventive effect against the manifestation of NIDDM. [Jpn J Physiol 54 Suppl:S236 (2004)]

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We examined the effect of rehydration on whole body and local sweating sensitivities during prolonged heavy exercise in a hot environment. Seven healthy male subjects performed 105 min of exercise on a cycle ergometer at 70% of VO₂max in a climatic chamber (Ta: 32°C, RH: 60%). The following three conditions were attempted: no rehydration (NR), rehydration in amounts equal to one-half of dehydration (R1), and rehydration in amounts equal to dehydration (R2). Tympanic membrane temperature (Tty), mean skin temperature (Tsk), total sweat loss (TSL) and local sweating rate (LSR) were measured. Whole body sweating sensitivity was calculated as a measure of TSL per degree rise in Tty. Local sweating sensitivity was defined as the slope of a regression line representing the individual LSR and Tty values obtained during the 0, 15 and 33 min exercise transient. Prolonged heavy exercise resulted in the degree of dehydration averaged 2.2, 1.1 and 0.1% BW during NF, R1 and R2, respectively, because of different rehydration levels. However, neither TSL nor LSR was different among all trials. The increased Tty was graded in proportion to the degree of dehydration whereas Tsk response was similar among all trials. Both whole body and local sweating sensitivities were decreased proportionally to the degree of dehydration, and were significantly higher in R2 than in NF. Thus the present study clearly demonstrates that rehydration attenuated the impairment of sweating sensitivity in a graded manner with increased rehydration levels during prolonged heavy exercise in a hot environment. [Jpn J Physiol 54 Suppl:S237 (2004)]

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[Objective]We examined the effects of long-term moderate exercise on cognitive brain function in older individuals using the P300 component of event-related brain potentials (ERPs).[Methods]Individuals from the active and sedentary group were matched by age (69.38 vs. 66.38 years) and sex (10 males and 10 females in each group). All subjects reported being free of neurological or psychiatric disorders, and provided informed consent. The subjects performed a somatosensory oddball task composed of pressing a button with their right foot as fast as possible following an electrical stimulus at the right index finger, and not responding following an electrical stimulus at the left index finger. The electroencephalogram (EEG) was recorded at Fz, Cz, and Pz according to the International 10-20 system referred to linked earlobes. [Results]The reaction time was faster for the active group (379.98 ms) than for the sedentary group (432.49 ms) (p<0.05). The P300 amplitude of the active group (11.11 μV) was significantly larger than that of the sedentary group (7.54 μV) (p<0.05). Moreover, P300 amplitude was maximum at the parietal site (Pz) in the active group, while the distribution of P300 became more distributed from the Pz to the frontal site (Fz) in the sedentary one. [Conclusion]Long-term moderate exercise had a positive influence not only on response processing but also cognitive processing for older adults. [Jpn J Physiol 54 Suppl:S237 (2004)]

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Effect of Exercise and Blood Volume on Plasma Volume ShiftKawabata T., T. Suzuki and T. MiyagawaDept. of Sport Medicine, Osaka City University School of MedicineThe aim of the present study is to assess the effect of exercise and BV on PV shift in individual variations. Thirteen well trained subjects participated in this study. BV, cardiac output and stroke volume were measured by the pulse dye densitometry using dye Indocyanine green. Subjects ran on the treadmill until exhaustion. Lactate threshold (LT), as a predictor of aerobic work capacity, was calculated from the exercise intensity at the point of plasma lactate concentration buildup to 4 mmol. Peak VO2, mean values (SEM), was 61.5(1.1) ml/kg/min. BV and PV were 64.7(3.9) and 38.1(2.4) ml/kg. The relationship of peak VO2 with BV and PV indicated a significant positive correlation. VO2 at LT was 57.5(1.5) ml/kg/min. The relationship of VO2 at LT with BV and PV indicated a significant positive correlation. The percentage of changes in PV during graded exercise decreased gradually from 10.7% to 20.7% in exhaustion. Shift in PV at LT level averaged 16.4% and the range of PV shift in individual variations were from 12.5% to 19.6%. The relationship of the changes in PV at LT with total BV and PV in individual variations indicated a significant negative correlation. These results indicated that 1) the relationship of peak VO2 with BV indicated a significant positive correlation, 2) the strong positive relation between shift in PV and total PV, and results in a maintenance of the circulating BV. [Jpn J Physiol 54 Suppl:S237 (2004)]

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During walking and running in human, evidence for the synchronization between cardiac and locomotor rhythm (CLS) has been demonstrated, but direct evidence showing the functional significance of such coordination has not yet been presented. One of explanations for the functional significance of CLS is enhancing cardiovascular efficiency. During locomotion, increased muscle tension produces an elevation of intramuscular pressure (IMP), and this often exceeds systolic pressures. Therefore, it is likely that the locomotor activity periodically occludes blood flow through active muscles. If the peak of IMP during locomotor activity were not to occur when the arterial pressure was highest the reduction of cardiac afterload and therefore ensuring of blood flow for active muscles would be expected. In the present investigation, I tested this hypothesis in nine healthy subjects by simulating the rhythmic IMP change using computer-controlled dynamic thigh cuff occlusion device. Alternate dynamic occlusions of bilateral thigh cuff administered at the frequency of mean heart rate produced the significant phase synchronization between heartbeat and occlusion rhythm. Heartbeats were most likely to occur at phases where the peak systolic pressure was not overlapped with the elevation of cuff pressure. These locking phases were comparable to those observed when walking cadence was voluntarily synchronized with mean heart rate. The results suggest that CLS may be associated with improving perfusion from heart to exercising muscles. [Jpn J Physiol 54 Suppl:S238 (2004)]

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We examined the hypothesis that the enhanced sensitivity of an increase in forearm skin vascular conductance at a given increase in esophageal temperature (ΔFVC/ΔT_es) during exercise after aerobic training would be caused by concomitant increases in blood volume (BV) and cardiac stroke volume (SV). Twelve male subjects (age, 21.3±0.7 (SE) yr; Vo_2peak, 58.0±0.8 ml·min⁻¹·kg⁻¹) exercised on a cycle ergometer at 60% Vo_2peak, 1 hr·day⁻¹, at 30°C of room temperature and 50% of relative humidity for 10 days. Before and after training, ΔFVC/ΔT_es was determined by having subjects perform 20-min exercise (EX) at 70% of pre-training Vo_2peak in the same environment. After training, BV at rest increased by 5.1±0.9 ml·kg⁻¹ (P<0.001) which was accompanied by an increase in SV of 0.31±0.05 ml·kg⁻¹ (N=10, P<0.001) at 10 min of EX. ΔFVC/ΔT_es determined after the onset of forearm skin vasodilation was 18.5±3.3 units·°C⁻¹ before training, increased to 31.6±4.2 units·°C⁻¹ after training (P<0.0001). The increase in ΔFVC/ΔT_es for individuals was correlated with the increase in SV at 10 min of EX (N=10, r=0.83, P<0.005), which was also correlated with BV (N=10, r=0.68, P<0.001). Thus, the increase in ΔFVC/ΔT_es after aerobic training may be enhanced by increased SV partially due to increased BV. [Jpn J Physiol 54 Suppl:S238 (2004)]

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Acute exercise activates the sympathetic nervous system, and catecholamines play a major role in the exercise-promoted lipid mobilization through adrenergic receptors (AR) which are expressed in adipocytes. Of several subtypes of ARs β-AR is coupled with the stimulatory G-protein (Gs), which activates adenylate cyclase, and in turn stimulates lipolysis. The aim of this study was to investigate the effect of acute exercise on β-AR-G-protein system in rat adipocytes. Adipocytes from epididaymal adipose tissue were isolated at 0, 3, and 24 h after acute exercise. Neither protein expression nor mRNA level in several types of Gsα was changed at each time point. However, protein expression of Gi2α which mainly inhibits adenylate cyclase activity decreased at 0 and 3 h, but it significantly increased at 24 h. In contrast, β-AR number increased at 0 and 3 h, but decreased at 24 h. In accordance with these phenomena, isoproterenol-stimulated cAMP productions increased at 0 and 3 h, but decreased at 24 h. Moreover, we investigate possible mechanism behind exercise-induced alterations in Gi2α protein. Proteasome activities were increased at 0 and 3h, but decreased at 24 h. Co-immunoprecipitation of Gi2α with ubiqutin was significantly increased at 0 and 3 h. The injection of lactacystin, a selective proteasome inhibitor, significantly increased Gi2α protein expression at 0 and 3 h compared with the value prior to exercise. These results suggest that ubiquitin-proteasome system regulates protein expressions of Gi2α. [Jpn J Physiol 54 Suppl:S238 (2004)]

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After training at high altitude, the effect on an individual endurance performance is varied. The purpose of this study was to investigate the effect of artificially increased dead space on the value of maximal oxygen uptake. Healthy male students sat for 5 minutes at rest and performed the graded sub-maximal exercise testing for 14 minutes using a treadmill including resting for 2 minutes twice, with or without artificially dead space of 820ml. The values of maximal oxygen uptake were estimated using the heart rate - oxygen uptake relation with the heart rate at 200 beats/min. The estimated maximal oxygen uptake with artificially increased dead space ranged widely from 87 to 56 percent of the maximal oxygen uptake without dead space as a control. These decreased values with dead space of 820 ml were equivalent to the reported values that were obtained in the environment at an altitude of about 2,550 - 5,000 meters. The observed percent of maximal oxygen uptake correlated with the percent of oxygen uptake with dead space/ control at the heart rate of more than 165 beats/min. The percent of maximal oxygen uptake correlated negatively with the percent of expiratory gas volume at the oxygen uptake of more than 1.5 l/min, in particular from the lower oxygen uptake levels. Therefore, the individual decline in oxygen uptake with dead space is caused by the individual decrease in ventilatory efficiency, and this method can be useful to determine an individual's capacity to adapt to high altitudes. [Jpn J Physiol 54 Suppl:S238 (2004)]

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The purpose of this study was to evaluate the relationship between the mental fatigue and the strength of physical exercise by event-related potentials (ERPs). Ten healthy college students (mean age: 20 years old) performed two kinds of multi steps exercise loading tests (hard test and soft test) using a treadmill. The loading strength was increased stepwisely until the heart rate of the subjects reached 90% of maximum in the hard test, and that was increased until the heart rate reached 70% of maximum in the soft test. In this study, audito EPRs and lactic acid in blood were adopted as mental fatigue and physical fatigue, respectively. Audito EPRs and the concentration of lactic acid in blood were measured just before and after the exercise in these tests. After these measurements, these parameters, were obtained every one hour for three hours. The latency of P300 in auditory ERPs was prolonged and the amplitude of P300 was decreased by the exercise loading tests. But, hard test and soft test differed each other in recovering patterns of the latency and the amplitude of P300. These results suggest that physical exercise can cause various levels of mental fatigue depending on the strength of physical exercise. However, the recovering patterns of the concentration of lactic acid in blood did not always coincide with recovering patterns of the latency and the amplitude of P300. The level of mental fatigue may not well related with the quantity of fatigue-products accompanied with a physical exercise. [Jpn J Physiol 54 Suppl:S239 (2004)]

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We previously reported that heat-shock protein (HSP) 70 content decreased in the soleus muscle atrophied by unloading and that such a decrease was inhibited by isometric resistance exercise (IRE) during unloaded condition. The present study was designed to investigate age-associated effect of IRE on preservation of muscle mass and HSP70 expression. Fischer-344 female rats (4-, 10-, and 20-month old) were assigned to either of control or hindlimb-unloaded (HU) group. Rats of HU group had their hindlimbs suspended for 3 weeks with or without IRE. IRE (stationary support on a flat wire mesh with 60~80 degree incline) was done for 30 min a day, 6 days a week, with an additional load of 30% body mass to the tail during HU period. Maximum force and myofibrillar protein content, and HSP70 were measured in the soleus muscle. Maximum force and myofibrillar protein content decreased significantly with HU and the degree of these decreases was greater with ageing. IRE inhibits these decreases by HU, but the inhibitory effect of IRE became lesser with advancing age. HSP70 content decreased by HU irrespective of age. IRE prevented decreases in HSP70 content and inhibitory effect of IRE became greater with aging. These findings demonstrate that preventive effect of IRE on muscle atrophy is associated with HSP70 expression but this interrelation is disturbed with aging. [Jpn J Physiol 54 Suppl:S239 (2004)]

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This study was designed to examine the changes in the capillary geometry and expression of VEGF receptors Flt-1(VEGFR-1) and Flk-1/KDR (VEGFR-2) in the left ventricles of female Wistar rats after endurance training with and without chronic CoCl₂ administration. The four groups of rats were non-treated sedentary, non-treated training, Co²⁺-treated sedentary and Co²⁺-treated training groups. Exercise training by running lasted for 5 weeks at 25 m/min on a 20% gradient, 10-60 min/day, 5 days per week. The Co²⁺ -treated rats drank water containing 0.01% CoCl₂ for 5 weeks. The Co²⁺ administration significantly increased the blood hemoglobin concentration by approximately 25% with and without training. In the subendocardium, both Co²⁺-treated groups with and without training significantly increased the capillary-to-myocyte ratio (C:M) whereas training alone did not. Training with Co²⁺ significantly increased the C:M ratio of arteriolar capillary. Although expression of VEGFR-2 protein was increased after Co²⁺ administration (by 59%) and training with Co²⁺ (by 46%), that of VEGFR-1and VEGF remained unchanged. These results suggest that chronic Co²⁺ administration facilitates capillary angiogenesis via VEGF system, but exercise training does not cause angioadaptation in myocardium. [Jpn J Physiol 54 Suppl:S239 (2004)]

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Regular exercise is known to result in reduction of fat tissue mass and serum leptin level followed by an increase in eating behavior. However, the effect of exercise on leptin receptor subtype-b (Ob-Rb) in the arcuate nucleus of the hypothalamus (ARC) has not yet been reported in old Wistar and OLETF rats. The purpose of this study was to investigate the effects of regular exercise on the expression of Ob-Rb mRNA in the ARC.
Male Wistar and OLETF rats were randomly assigned to either the exercise or control group, respectively. At 26~38 weeks, exercising rats housed freely accessible running wheels and all rats were provided with water and chow food ad libitum.
Chronic voluntary exercise remarkably reduced fat tissue mass and blood leptin level in both Wistar and OLETF rats. In Wistar rats, no change was observed with regard to food intake, and this demonstrated leptin resistance. There was a significant decrease in gene expressions of Ob-Rb in the ARC. On the other hand, exercise did not influence the hypothalamic Ob-Rb mRNA expression and resulted in a remarkable elevation of appetite in OLETF rats. The present findings suggest that de-sensitive regulation of leptin induced by long-term exercise might lower the signal of fat volume change to regulate food intake in old Wistar rats, but not in obese and hyperphagic OLETF rats. [Jpn J Physiol 54 Suppl:S239 (2004)]

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Long-term cold exposure to Zucker fatty rats resulted in good effects on lipid metabolism and suppression of weight-increment through growth. We investigated the effect of cold environment on energy balance of OLETF rats, another obese strain. Methods: Male OLETF and LETO rats aged 7 weeks were housed at 10°C or 25°C for 11 weeks (cold acclimated, control) and 25°C for 2 weeks after acclimation to 10°C for 9 weeks (deacclimated). Changes in body masses and food intake and oxygen uptake at 10°C and 25°C were measured. Brown adipose tissues (BAT) were isolated after 11 weeks acclimation and mass value, morphological change and expression of proteins in BAT were analyzed. Contrary to Zucker fatty rats, amounts of food intake of OLETF rats during cold exposure were markedly increased and those of oxygen consumption at 10°C were higher and were comparable to those of LETO rats. Changes in mass value and lipid content of BAT showed similar tendency as those of Zucker fatty rats but absolute values of mass were smaller. Sizes of lipid droplets of BAT were significantly smaller than those of Zucker fatty rats, though larger than those of LETO rat. These results indicate that energy expenditure of OLETF rats is greater and BAT are more active than those of Zucker fatty rats though amount of food intake is remarkably increased. Expressions of many proteins isolated from BAT were changed through cold acclimation and deacclimation and these were somewhat differed from those of Zucker rats. [Jpn J Physiol 54 Suppl:S240 (2004)]

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To assess the effect of mean skin temperature (T_sk) on active cutaneous vasodilator system, we measured skin sympathetic nerve activity (SSNA) from the peroneal nerve by microneurography during mild heat stress in 6 subjects. Skin blood flow (SkBF; laser-Doppler flowmetry) was investigated at the bretylium treated and untreated sites on the dorsal foot while monitoring sweat rate (hygrometer) at the pilocarpine treated site and mean arterial pressure (MAP; Finapres) from the middle digit. Subjects kept semi-recumbent position and wore a thermal suit perfused with warm water at 34°C, raised to 36, 38, and 40°C every 30 min. All data were collected for the last 10 min of each stage. T_sk increased from 34.8 ± 0.2°C at 34°C to 35.7 ± 0.2°C at 40°C (P<0.05) by 0.2 - 0.3°C every stage, without a change in esophageal or foot skin temperature during the first 3 stages. Cutaneous vascular conductance (CVC; SkBF/MAP) at bretylium treated site increased by 48 ± 22% at 38°C and 70 ± 23% at 40°C compared to 34°C (P<0.05). The number of sweat expulsions during 10 min increased from 30 ± 1 at 34°C to 41 ± 4 at 38°C (P<0.05) and 49 ± 6 at 40°C (P<0.05). Burst rate of SSNA increased from 11 ± 2 bursts/min at 34°C to 17 ± 3 bursts/min at 40°C (P<0.05). The amplitude of SSNA burst increased at 38 and 40°C (P<0.05) while reducing duration (P<0.05). Thus, the change in the burst pattern of SSNA at 38 and 40°C suggested the involvement of active vasodilator and/or sudomotor activity which were modulated by the rise in T_sk. [Jpn J Physiol 54 Suppl:S240 (2004)]

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To clarify exercise training-mediated alteration in blood vessel tone, the relation between exercise training and human vascular tone was assessed with analyzing alteration in pulsatile arterial function. Arterial pressure pulse waveforms of healthy students (n=182) in Shimane University Faculty of Medicine were recorded by using a modified Windkessel model and characterized waveform morphology to determine large (C1) and small (C2) arterial elasticity compliance during the diastolic portion of the cardiac cycle. Data were compared between students belonging to exercise training clubs (Ex: n=112) and to non-exercise training clubs (NEx: n=70). The values of C1 and C2 of Ex students were 17.2±0.4 mL/mm Hg and 9.2±0.2 mL/mm Hg, respectively, and significantly increased by 6.5% and 14.7% compared with those of NEx students. Diastolic blood pressure and the systemic vascular resistance were significantly lower in Ex students than in NEx students and inversely pulse pressure higher. C2 was positively correlated with diastolic blood pressure. It is suggested that an increase in systemic C2 indicates the improvement of endothelial function on small arterial tone. Data from the students may represent that exercise training has reversible beneficial effects on cardiovascular diseases such as hypertension with endothelial dysfunction accompanied by functional and structural changes that influence arterial stiffness. [Jpn J Physiol 54 Suppl:S240 (2004)]

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Hot compresses in the lumbar region are empirically known to ameliorate patient complaints of constipation and abdominal fullness. We have previously shown that warming the lumbar skin increases the interdigestive migrating motor complex (IMC) of the stomach in humans. The activity of vagal nerves is decreased by warm stimulation, and the action of splanchnic sympathetic nerves is inhibitory on the gastric motility. Therefore, we have provided a hypothesis that vasoconstriction and redilatation in the abdominal arteries induced by lumbar skin warming activate IMC of the stomach. To confirm this hypothesis, we examined the effect of lumbar skin warming (42°C, 10 min) on diameters of the abdominal aorta and coeliac artery (DAA and DCA) in healthy humans, employing an ultrasound imaging of these arteries. In the test group with lumbar skin warming, DCA during stimulation did not differ from DCA at rest. However, DCA post-stimulation was increased by 17%. DAA was not affected by warming. In the time-matched control group without warm stimulation, both DCA and DAA remained unchanged. It is therefore concluded that lumbar skin warming causes vasodilatation of the coeliac artery. The timing of the increase in DCA well coincided with that of the increase in IMC previously reported. This shows that an increase in gastric blood flow and the activation of IMC are induced together by lumbar skin warming, although a possibility of vasoconstriction preceding vasodilatation is still to be explored. [Jpn J Physiol 54 Suppl:S241 (2004)]

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Anxiety is defined as an over-arousal state, and anxious patients complain of a variety of physical symptoms. Concerning the maintenance of balance, a correlation between anxiety and postural instability is suspected. Therefore, we examined whether anxiety correlates the parameters of balance control in healthy college students employing a within-subject paradigm. State anxiety and body sway were measured twice with an interval of a month. Anxiety was scored by Spielberger's state-trate anxiety inventory just before the experiment. Body sway of each participant was then recorded for first with eyes open and next with eyes closed. Correlations between the changes in state anxiety and parameters of body sway were examined by Pearson's correlation analysis. Changes in enveloped area of body sway (ENV) and in maximum length of the antero-posterior body sway (YML) showed positive correlation with changes in state anxiety (ENV: r=0.534, p=0.013; YML: r=0.659, p=0.001). Data showed that an increase in anxiety caused an instability in the control of postural balance. These correlations were abolished when the eyes were closed. In conclusion, an increase in state anxiety caused an instability of postural balance in antero-posterior axis and increased the area of body sway. A possibility is raised that state anxiety affects the processing of visual inputs and influences the net performance of the postural control. [Jpn J Physiol 54 Suppl:S241 (2004)]

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The central chemoreceptor neurons of the mammals were thought to be distributed over the ventral medullary surface (VMS) that is bathed in cerebrospinal fluid, and are stimulated by excess H⁺ to induce a hyperventilation. Using a voltage-sensitive dye, DiBAC4(3), we found the low dose of PCB (1 microM, Aroclor 1254) effects on the excitability of H⁺-sensitive neurons derived from the newborn rat VMS. In this study, we investigated that the effects of hydroxy PCB (4-OH-2',3,3',4',5'-pentachlorobiphenyl) on intracellular calcium concentrations ([Ca²⁺]_i) in cultured neurons derived from the newborn rat VMS. To monitor [Ca²⁺]_i in cultured neurons, we performed microfluorometric measurements using the fluorescent probe Fluo 3-AM. Expose of cultured neurons to hydroxy PCB dose-dependently increased [Ca²⁺]_i . Cultured neurons exposed to 10, 50 and 100 nM hydroxy PCB showed increases in [Ca²⁺]_i which were at exposure times of 10 min. Higher dose of hydroxy PCB (1 microM) reduced [Ca²⁺]_i in the cultured neurons compared to elevations seen following exposure to 100 nM hydroxy PCB. The increase of [Ca²⁺]_i in the hydroxy PCB solution was blocked with L-type Ca²⁺ channel blocker (10 microM nimodipine). These results suggest that the low dose of hydroxy PCB increases [Ca²⁺]_i in cultured VMS neurons via a mechanism through L-type Ca²⁺ channels. [Jpn J Physiol 54 Suppl:S241 (2004)]

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The aim of this study was to clarify neurological cause of the human disorder such as multiple chemical sensitivity and sick building syndrome, which is related to chronic exposure to low dose of volatile organic compounds (VOC). We chose toluene (Tol) and formaldehyde (FA) as VOC, and evaluated hippocampal CA1 synaptic transmission as a parameter of neurological memory function. In the case of Tol exposure, male C3H/He mice (8-wk old, n=5) were restrained to keep nose inserted into a chamber filled with 90 ppm Tol for 30-min, 7 times within 4-wk. In the case of FA exposure, female C3H/He mice (8-wk old, n=10) were exposed to 400ppb FA in a FA conc.-controllable chamber for 16-h a day, 5-d a week, for 12-wk. Within a few days from the last inhalation, each mouse was decapitated and hippocampal slices were prepared from the middle third of the hippocampus. By stimulation of Schaffer collaterals, field potential was recorded from stratum radiatum. Two parameters, I/O relationship of fEPSP and LTP induced by theta burst tetanic stimulation, were compared between exposed and control groups, and no significant difference was observed. Our results suggest that residential exposure to VOC do not influence hippocampal synaptic transmission in human. [Jpn J Physiol 54 Suppl:S241 (2004)]

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Underground water in Mt. Fuji area is enriched with vanadium, and drinking water contains vanadium with concentrations varying between 0.06 and 0.10 mg/L . In cultured cells, vanadium has been reported to activate insulin-receptors and facilitate the utilization of glucose. Therefore, anti-diabetic effect of vanadium is widely expected. However, the effect of vanadium at concentration of tap water level (VTL) to decrease blood glucose has not yet been confirmed in animal experiments, and thus its physiological action remains unclear. To examine whether VTL affects the taste sense, we compared taste thresholds to glucose, proline, and hydrogen chloride. Participants were healthy college students without a habit of smoking. They were requested to report recognition threshold of these substances after they tested them with and without vanadium in distilled water at least 2 h after their breakfast or lunch. Coexistence of 0.1 mg/L vanadium decreased threshold concentration of glucose by 25%. Sweet taste threshold to proline was not affected by vanadium at 0.1 mg/L but decreased by 1.0 mg/L vanadium. Sour taste threshold to hydrogen chloride was not affected by vanadium either at 0.1 mg/L or 1.0 mg/L. Sweet taste threshold to glucose was influenced by VTL rather specifically. We have identified one of the physiological roles of VTL. It is possible that vanadium facilitates a mechanism which sensitizes taste cells responding to glucose. [Jpn J Physiol 54 Suppl:S242 (2004)]

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We investigated the influence of environmental enrichment on newly born cells after 6-hydroxydopamine (6-OHDA) injection into the striatum. Male Wistar rats (P25) were housed in normal cages (18x23x40cm, 2-3 rats per cage) or environmental enrichment cages (81x51x53cm, with enriched apparatus, 6-7 rats per cage) for 1 week. Then 6-OHDA (20μg) was injected into the left striatum, and then rats were kept under each circumstance to the end of experiment. To label proliferating cells, the animals were received BrdU (daily, 50mg/kg body weight, i.p.) for 3 days just before fixation at 1 or 2 weeks after 6-OHDA injection. Coronal sections (40μm) were counted (n=7-10) for BrdU-positive (BrdU+) cells in the subventricular zone (SVZ) and the striatum near SVZ (STR). In the SVZ, the number of BrdU+ cells significantly decreased 2 weeks after the lesion in both groups (63.7±7.3 to 45.5±5.4 in normal condition-groups, 76.0±6.8 to 51.3±4.4 in enriched groups). In the STR, BrdU+ cells increased 1 week after the lesion in both groups (12.1±1.5 in control, 18.9±1.9 for lesions in normal condition-groups, 16.7±2.73 for lesions in enriched groups). Although BrdU+ cells significantly decreased to control level 2 weeks after the lesion in normal condition-groups (9.7±1.34), the number of BrdU+ cells remained high in enriched groups (14.4±3.0). Data suggest that the production of BrdU+ cells, 2 weeks after 6-OHDA injection into the striatum, remained in the STR but not in the SVZ under environmental enrichment. [Jpn J Physiol 54 Suppl:S242 (2004)]

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Microgravity shifts body fluid to upper body during spaceflight. And the survival ratio of rat newborns after spaceflight is low, however, why newborns died in space is still unclear. They imply that the postnatal development is the key to realize generation transition in space. The aim of this study is to examine the structural development in kidney macroscopically.Eight- and 14-day old rats were launched at these ages in the Space Shuttle Colombia for 16 days (STS-90; Neurolab). Some of 8-day rats were reared on the ground for 30 more days after landing as the re-adaptation group. Six of 11 flight rats of the 8-day group showed ambilateral hydronephrosis. Despite the hydronephrosis and tubule expansion existed, it was thought that these kidneys were potentially functional in filtration process. This hydronephrosis was remained in the re-adaptation group, but it wasn't observed in the 14-day group.Here we found that spaceflight brings about acquired ambilateral hydronephrosis during the second week of life. This result suggests that the failure of urine transportation that occurs in upper urinary tract because of weightlessness. [Jpn J Physiol 54 Suppl:S242 (2004)]

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In a variety of mammals, the spatial ability is better in males than in females, and the activity in the novel environment is less in males than in females, and these sex differences have been believed to be genetically determined. In the present study, we examined whether the sensory stimuli brought about by chewing diet affected the spatial ability and the activity in the novel environment. We confirmed that, in rats fed a standard laboratory hard diet, male rats performed better than female rats in the radial arm maze task and exhibited less activity than female rats in the open field task, as previously shown. We however found that, in rats fed a soft diet, sex difference in the radial arm maze task was not found, in association with increases in the expression of NMDA receptor subunit R1 mRNA in the hippocampus and in the amount of acetylcholine release in the prefrontal cortex in female rats. There was no change in the sex difference in the open field task. We conclude that constitution of diet during development affects some aspects of cognitive functions, but not emotional functions. One is better to pay attention what environmental conditions are good for both sex. [Jpn J Physiol 54 Suppl:S242 (2004)]

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The exact mechanism for weather change-induced pain has not been clarified. We have demonstrated that lowering barometric pressure (27 hPa over 8 min) augments pain-related behaviors of rats rendered neuropathic by chronic constriction injury (CCI) to the sciatic nerve. In the present experiment, we introduced a new pressure chamber, which can induce lowering barometric pressure in a variety of rates, and with this chamber we tested whether lowering barometric pressure at slower decompression rates influence CCI-induced neuropathic pain in rats. To measure mechanical hyperalgesia, noxious bending force (92.2 and 197.2 mN) of von Frey hairs (VFH) were applied ten times to the plantar skin, and the number of foot withdrawals was counted. Withdrawal thresholds to the VFH stimulation were also measured. When the CCI rats were exposed to lowering barometric pressure (20 hPa lower than atmospheric pressure; LP) at the rates of 1.4, 0.67 and 0.33 hPa/min, the already increased number of foot withdrawals in response to these mechanical stimuli (hyperalgesia) was further increased, and the already decreased withdrawal threshold was further decreased. LP at the rate of 0.17 hPa/min increased the mechanical hyperalgesia to 197.2 mN VFH, and decreased the threshold. On the other hand, LP at the rates of 0.13 or 0.06 hPa/min did not influence the mechanical hyperalgesia or the threshold in CCI rats. These results show that decompression rate must be more than 0.17 hPa/min so that augmentation of neuropathic pain is caused. [Jpn J Physiol 54 Suppl:S243 (2004)]

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A new heat escape behavior was revealed in mice under acute heat stress condition. Mice were exposed to each condition of 24, 34, 37 and 38.5°C for 60 min. Rectal temperature increased under the 34°C condition, and under 37 and 38.5°C conditions serum osmolality and body weight loss also increased. A large number of mice exposed to above 37°C attempted to escape from the partially covered cage, and so exhibited jumping behavior during the 60 min. But, mice exposed to 24 and 34°C did not. These results indicated that acute heat stress above 37°C induced evaporative water loss and jumping escape behavior in mice. [Jpn J Physiol 54 Suppl:S243 (2004)]

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We examined whether cardiovascular and oxidative stress responses during mild mental stress change depending on plasma estradiol concentrations. Eight healthy young women (YW, mean±SD age 23.1±0.4 years) and 8 healthy postmenopausal women (PMW, 55.8±1.5 years) underwent mental and physiological stresses, which were evoked by Stroop Color Word Test (CWT) and handgrip, respectively. In young subjects, the experiments were repeated at two different phases of their menstrual cycle (M: menstrual phase, F: follicular phase). Blood Pressure, heart rate, skin blood flow (forehead, forearm) and mental sweating were measured continuously before, during and after the two stresses. Venous blood samples were taken for the measurement of plasma catecholamine, nitric oxide metabolites (NOx), 4-hydroxy-2-nonenal (HNE) and estradiol concentrations. The resting mean arterial pressure (MAP) was higher in PMW compared with in YW at both phases. There was no significant difference in CWT-induced MAP elevation between YW at both phases and PMW. However, MAP returned to the resting level sooner in F than M and PMW. CWT-induced elevation of forehead skin blood flow was enhanced in F compared with M and PMW. The resting level of plasma HNE concentration was higher in PMW than F and M. These findings suggest that estrogen has an effect of mediating vascular and oxidative stresses at rest and during stress. [Jpn J Physiol 54 Suppl:S243 (2004)]

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We assessed the hypothesis that chronic estrogen replacement in ovariectomized rats suppresses cardiovascular responses to cage-switch stress by attenuating plasma norepinephrine (NE) release and increasing nitric oxide (NO) production in peripheral vascular bed. Adult ovariectomized rats were randomly assigned placebo-treated (P) or estrogen-treated (E) group and implanted with pellet containing either placebo or 17β-estradiol (1.5 mg/60-day release). After four weeks, to collect blood samples they were catheterized with cannulae into jugular veins. After recovery, rats were exposed to the cage-switch stress for 30 min. Each rat underwent the stress 24h after administration of plain tap water or NG-nitro- L-arginine methyl ester (L-NAME)-supplemented water (250μg/ml in water). Blood samples were collected at rest and at 30 min after the start of the stress. Mean arterial pressure and heart rate responses to cage-switch stress were significantly attenuated in the E group compared with the P group, but the difference disappeared after pretreatment of L-NAME. Stress-induced plasma NO elevation was suppressed after L-NAME in the E group. On the other hand, the surge of plasma NE during the stress was diminished in the E group, but not in the P group. [Jpn J Physiol 54 Suppl:S243 (2004)]

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Our recent study showed that chronic estrogen replacement in ovariectomized rats has the beneficial effect of suppressing stress-induced cardiovascular responses. However, the mechanisms involved are unknown. We used mild psychological stress evoked by cage-switch, and addressed the hypothesis that estrogen alters the stress-induced expression of c-Fos, a marker for neuronal activation in response to stress, in the brain of ovariectomized rats. Adult female rats were randomly assigned placebo-treated (P), estrogen-treated (E) and normal female (C) groups. The P and E groups were ovariectomized and implanted with pellets containing either placebo or 17 b-estradiol (1.5 mg/60-day release). Each group rat underwent cage-switch or immobilization stress for 30 min and was sacrificed at 60 min after the cessation of the stress. The rats were perfused, and the brains were extracted and immediately frozen. Stress-induced c-Fos expression was analyzed quantitatively by immunohistochemistry. C-Fos expressions were detected in the hypothalamic paraventricular nucleus (PVN), amygdala and arcuate nucleus in the rat forebrain subjected to cage-switch stress. In PVN and amygdala, c-Fos expression changed depending on the type of the stresses. Moreover, c-Fos expression in these regions tended to decrease in the E group compared with P group. These findings suggest that estrogen affects c-Fos expression induced by the mild psychological stress in rat forebrain. [Jpn J Physiol 54 Suppl:S244 (2004)]

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The purpose of this study was to examine input mechanism which is related to the bradycardia observed during artificial CO₂ bathing in anesthesia rats. 12 male rats of the Wistar strain were used in the experiments. The rat was medicated with urethane anesthesia (1.39-1.60 g/kg). Arterial blood pressure, heart rate, tissue blood flow, pH, PaO₂, PaCO₂ and temperature of the immersed skin, and rectal temperature were continuously measured. Bath water exchanged for another, i. e. tap water (10-20 ppm CO₂)into CO₂ water (965-1400 ppm CO₂) or vice versa, every about 30 min. Water temperature was controlled at 35°C. To confirm the effect of CO₂ inhalation on the heart rate and blood gases during immersion, CO2-mixed gas (5% CO2, 20% O₂, 75% N₂) instead of fresh air was supplied into the face mask, and hemodynamic parameters and blood gases were measured. In the operation, a midline incision (about 2 cm) was made on the dorsal skin over the thoracic vertebrae (T₂-T₆), and the dura matter was exposed between T₄ and T₅ in 6 animals with above mentioned probes. No effect blood gas responses were observed in anesthetized rats during CO2-water immersion. In a mixture of 5% CO₂ inhalation, HR and blood gas parameters were significantly increased on tap water and CO₂-water. HR was significantly lower in CO₂-water than in tap water at sham operated, but was roughly equal at spinal cord transaction. This results suggested that the expression of the bradycardia is not generated through chemoreceptors such as the carotid artery corpuscle. [Jpn J Physiol 54 Suppl:S244 (2004)]

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An otolith organ on ground behave as a detector of both gravity and linear acceleration, and play an important role in controlling posture and eye movement for tilt of the head or translational motion. On the other hand, a gravitational acceleration ingredient to an otolith organ disappears in microgravity environment. However, linear acceleration can be received by otolith organ and produce a sensation that is different from that on Earth. It is suggested that in microgravity signal from the otolith organ may cause abnormality of posture control and eye movement. Therefore, the central nervous system may re-interprets all output from the otolith organ to indicate linear motion. A study of eye movement has been done a lot as one of a reflection related to an otolith organ system. In this study, we examined function of otolith organ in goldfish revealed from analysis of eye movement induced by linear acceleration and/or the tilt of body. We analyzed both torsional and vertical eye movements from video images frame by frame. For tilting stimulation, torsional eye movements induced by head down was larger than that induced by head up. For acceleration stimulation, torsional eye movements induced during head down was larger than that induced during head up. These results suggest that body tilt and linear acceleration may not be with equivalent stimulation to cause eye movement on the ground. [Jpn J Physiol 54 Suppl:S244 (2004)]

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We examined the effect of countermeasure, including artificial gravity and ergometric exercise, in 10 young healthy men before and after 20 days of bedrest. We loaded 20 min of hypergravity with low intensity exercise and 20 min of low gravity of 0.3 G with high intensity exercise (80% of V_O2max) for 10 days. The load has been proved to be effective on myatrophy and physical fitness, however, the effects on orthostasis and osteoporosis were attenuated. Development for the protocol for all systems, cardiovascular, skeletal muscle, and bone metabolism shall be projected in the future stusies. [Jpn J Physiol 54 Suppl:S244 (2004)]

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Exposure to cold potentiates cell proliferation and differentiation in brown adipose tissue (BAT) by activating the sympathetic nerve systems, and causes an increase in mitochondrial biogenesis as well as the activation of genes encoding several proteins. We investigated the expression of proteins on Xenopus laevis oocytes injected with total RNA purified from the cold acclimated BAT by immuno electron microscopy, and further the induction in UCPs (UCP1, 2, 3) in the BAT after cold acclimation of rats by Real-Time PCR technique.
Total RNA from rat interscapular BAT of warm- or cold-acclimated rats was extracted using the AGPC method. RNA was digested with RNase-free DNase to remove eventual traces of genomic DNA. mRNA was isolated by poly A selection and then double stranded cDNA was synthesized. Immuno-gold electron microscopy using anti UCP polyclonal antibody revealed the localization of immuno-gold particles on the inner membrane of mitochondria like structure of the newly synthesized membrane in the oocytes injected with the cold acclimated rat transcript. Real-Time PCR assay that combines TaqMan technology with fluorescent-based high resolution capillary electrophoresis and GeneScan DNA fragment analysis was applied for detection and quantification of BAT UCP mRNA. Real-Time assays were performed using primers corresponding to conserved domains of rat UCP1, UCP2 and UCP3. The result revealed that UCP2 transcripts were elevated in the RNA fraction purified from BAT of cold acclimated rats than that of warm acclimated rats. [Jpn J Physiol 54 Suppl:S245 (2004)]

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We examined to investigate the sensory conflict theory hypothesizing for the space motion sickness. In the last meeting, we reported results of equilibrium tests while subjects were exposed to simulating condition using reversing prisms; shift of deviation angle in vertical writing test, elongation of total length and start-end distance in square drawing test. Under the reversing visual conditions, moreover, transitional positions of stepping test were localized similarly to those under blindfolded condition. Statokinesigram detected slight increases in trajectory length and enveloped area, decrease in Romberg ratio, and an increase in power spectrum ratio. These modifications were more significant in right-left reversing prisms than in up-down inversing ones. Therefore the reversing prisms were more suitable for simulating experiment in the space motion sickness than inversing prisms. In the present study, we investigated cardiac responses and electrogastrography (EGG) during simulating condition caused by reversing prisms. Experimental protocol was quite same as the previous reports. Only 7 of all 21 subjects completely tolerated for 6 hours. Their chief complaints were nausea, vertigo and a headache. Intolerable subjects revealed an increase of low frequency (LF) of R-R interval, a decrease in high frequency (HF), and an increase of LF/HF. We discuss effects of reversing prisms upon the cardiac responses as well as EGG, and also partly refer to mechanisms of space motion sickness. [Jpn J Physiol 54 Suppl:S245 (2004)]

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To examine the effects of change in meteorological factors on autonomic parameters in conscious animals, male Sprague-Dawley rats (n = 11) were exposed to lowering barometric pressure (LP) in a climate-controlled room. Systemic blood pressure (BP) was telemetrically recorded using a radio-transmitter equipped with a BP transducer. Heart rate (HR) was calculated from BP data and pulse interval variability was analyzed by power spectrograms obtained by the fast-Fourier transform algorithm. The low-frequency (LF: 0.02-0.6 Hz) power, high-frequency (HF: 0.8-3.0 Hz) power and LF/HF ratio, an index of relative sympathetic activity, were calculated. The rats were exposed to LP by decreasing the barometric pressure of the room by 27 hPa lower than the atmospheric pressure. This was done over 8 min. The pressure was maintained at this level for 29 min, and then returned to the baseline pressure over 8 min. The BP markedly increased after reaching the pre-set low pressure and reached the peak value at the middle of LP-exposure period. The HR and LF/HF ratio clearly rose in the early part of the LP-exposure period and then gradually decreased to the level before exposure. The LF/HF ratio also transiently increased at the recompression period. These results show that lowering barometric pressure within the range of natural environmental fluctuation induces autonomic responses in conscious rats. The increase in the LF/HF ratio during LP exposure indicates that low pressure environment induces sympathetic > parasympathetic activation. [Jpn J Physiol 54 Suppl:S245 (2004)]

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Adrenomedullin (AM) is a multifunctional peptide involved in regulation of cerebral circulation and blood-brain barrier function. Recent studies suggest the protective effects of AM on ischemic brain damage. Effects of AM on cerebral edema, however, have not been investigated. The present study was aimed to investigate the effects of AM and its receptor antagonist, AM_22-52, on ischemia-induced cerebral edema in rats using magnetic resonance imaging. Rats were subjected to 1 h of middle cerebral artery occlusion (MCAO) followed by reperfusion. Intravenous injection of AM (1.0 μg/kg), AM_22-52 (1.0 μg/kg), or saline was made before MCAO. One day after the surgery, total edema volume, as well as hemispheric swelling, was greatly and significantly reduced by pre-treatment with AM (reduced by 53.2%). The protective effect of AM against edema was more clearly observed in the cerebral cortex (reduced by 62.7%) than the striatum (reduced by 30.7%). Post-treatment with AM had no effects. Pre-treatment with AM_22-52 tended to exacerbate the edema. The present study clearly suggests the protective effect of AM against cerebral edema, especially the cortical edema, in rat stroke model. [Jpn J Physiol 54 Suppl:S246 (2004)]

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Electrical stimulation of the vagus nerve (VNS) has shown efficacy in neuropathological conditions such as seizures and ischemia. However, its protective mechanism has been poorly examined to date. The present study was designed to clarify the mode of action of VNS in cerebral ischemia. Left VNS (0.4 mA, 40 Hz) was performed during 5-min ischemia in gerbils. The number of normal neurons in the bilateral CA1 subfield was counted 1 week after ischemia. In addition, extracellular glutamate and cerebral blood flow (CBF) in the dorsal hippocampus were measured using a dialysis electrode and a laser Doppler probe, respectively. Almost all neurons were killed by the 5-min ischemia in the Isch group. About 50% of the hippocampal neurons were rescued from ischemic insult by VNS, and this effect was prevented by transection of the vagus nerve centrally to the site of cervical stimulation. VNS significantly attenuated both ischemia-induced glutamate release and transient increase of hippocampal blood flow during reperfusion. Hyperemia as well as excessive glutamtate release after iscehmia is regarded as important factor in ischemic brain damage as it leads to generate considerble reactive oxygen spieces. Thus, VNS might protect neurons from ischemia-induced glutamate excitotoxicity and reperfusion injury via the afferent pathway of the vagus. [Jpn J Physiol 54 Suppl:S246 (2004)]

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Spatio/Temporal Regeneration of Oligodendrocyte Progenitor Cell after Spinal Cord Injury in Adult RodentsDi Wu1, Sei Shibuya1, Osamu Miyamoto2, Toshifumi Itano2Departments of Orthopaedic Surgery1 and Neurobiology2, Faculty of Medicine, Kagawa University In adult mammals, differentiation and regeneration of oligodendrocyte progenitor cells do happen after SCI. In this study we analyzed the NG2 expression after SCI, which is the specific marker for oligodendrocyte progenitor. SD rats had a laminectomy at Th11-12, spinal cord contusion was created by compression with 30 g of force for 10 min. Animals were examined at 24 h and 1, 4, 8 and 12 weeks after injury. 20-μm-thick frozen sections were prepared. Immunohistochemical staining was performed using antibody to NG2. At 4 weeks after injury, NG2 (+) bipolar oligodendrocyte progenitor with arborizing processes had spread throughout the white matter from below the pial surface. At 8 weeks after injury, NG2 expression reached the peak which was 5-fold greater than that in control group. NG2 expression was also observed in the gray matter around the central canal, and was especially strong around the ependymal cells at 8 weeks after the injury which was 4-fold greater than that in the control group. The present study showed that oligodendrocyte progenitor cells divide and migrate from subpial astrocytes. This may be the special mechanism in neural repair and regeneration after SCI in adult mammals, which is different from that in embryonic stage. [Jpn J Physiol 54 Suppl:S246 (2004)]

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To investigate spinal cord function following hypertension in M-SHRSP, spinal reflex evoked by magnetic stimulation was recorded in the tibiallis anterior muscle and the histological changes were observed before and after paralysis apperance. Recording of magnetically evoked EMGs activity corresponds to H-reflex and M-responses, allowing examination of the neuronal states of the spinal cord. Acceleration of the F-wave and a reduction in the amplitude of the H-reflex observed even before paralysis apperance. The thresholds of the M-response shifted after paralysis apperance. The pathological studies showed that spinal hypertensive vascular lesions were detected in 79% and 93% of the before and after paralysis apperance in M-SHRSP, respectively. In WKY and SHR, magnetically evoked EMGs and pathological lesions were not detected in spinal cord of any of the 6 weeks to 25 weeks old rats. These results indicated that changes in associated with muscular action in the spinal cord precede the development of morphologic changes of the spinal cord. Spinal reflex evoked by magnetic stimulation was a very useful method for detecting spinal hypertensive vascular lesions. [Jpn J Physiol 54 Suppl:S247 (2004)]

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ATTENUATING EFFECT OF FLECAINIDE ACETATE ON HERPETIC PAIN IN MICE INFECTED WITH HERPES SIMPLEXVIRUS.Asano K., Asahina S., Sakai M., Hisamitsu N., Oomori T., Hisamitsu T.Department of Physiology, School of Medicine, Showa University, Shinagawa-ku, Tokyo The influence of flecainide acetate (FA) on herpes-related pain responses was examined using mice infected with herpes simplex (HSV). BALB/c mice inoculated with HSV on the hind paw showed decrease innociceptive threshold, which appeared in the hind paw on the inoculatedside on day 6. Intraperitoneal adminstration of FA, a human injection grade,prevented decrease in nociceptive threshold dose-dependently in HSV-inoculated mice, which was firstly observed at a dose of 75 mg/kg, and peaked at doses more than 100 mg/kg. This antinociceptive effect of FA was attained peak at 60 min after administration and declined gradually to non-treated levels by 180 min.Intraperitoneal administration of FA at a dose of 100 mg/kg caused significant increase in b-endorphin (BE) levels in mid brain and hypothalamus from HSV-inoculated mice. These results strongly suggest that FA exerts antinociceptive effects on herpes-related pain through enhancement of BE levels in central nerveous system in HSV-inoculated mice. [Jpn J Physiol 54 Suppl:S247 (2004)]

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It is known that H-reflex is reduced in patients with Parkinson's disease. In the present study, we used a hemi-Parkinson's disease model to investigate the mechanism of the changes of H-reflex in Parkinson's disease in rats. In addition, the effect of L-dopa on the changes of H-reflex in the model was also observed. The hemi-Parkinson's disease model was achieved by administration of 6-OHDA into left medial forebrain bundle in male Wistar rat. The experiments were conducted two weeks after 6-OHDA administration. The H and M waves evoked by stimulation of sciatic nerve were recorded in both sides of the 5th digit of the hind limb. The threshold ratios of evoked H and M waves were compared before and after injection of L-dopa (100 mg/kg, ip). The results showed that the contralateral threshold ratio of H/M (1.782±0.361) was significantly higher (p<0.01) than that of ipsilateral one (1.346±0.265). After injection of L-dopa, the contralateral threshold ratios of H/M were gradually decreased and reached a significantly lower value (1.316±0.271; p<0.05) at 120 minutes after L-dopa injection. The higher values of contralateral threshold ratio of H/M in Parkinson's rats were supposed the result of depression of H-reflex excitability. The improvement of high threshold ratio of H/M by administration of L-dopa suggested that the absence of dopamine decreases the excitability of peripheral H-reflex. We concluded that the reduction of alpha motor neurons excitability by lacking of dopamine in Parkinson's disease may enhance the reciprocal or recurrent inhibition. [Jpn J Physiol 54 Suppl:S247 (2004)]

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We investigated peripheral leukocyte subpopulations using flow cytometry in mouse collagen-induced arthritis (CIA), one of the most-established model of rheumatoid arthritis. DBA/1J male mice were immunized 200 μg of heterologous type II collagen (CII) emulsified in CFA and boosted with the same dose of CII plus IFA 21 days later. Freshly isolated peripheral leukocytes from intact and CIA mice on day 35 and 42 after the first immunization were stained with corresponding mAbs and FITC- or PE- conjugated mAbs. Flow cytometry was performed using FACSCan (BD Biosciences). On day 35, we detected an increased number of leukocytes and an increased proportion of granulocytes. Therefore, the percentage of lymphocytes decreased, but the number of them slightly increased. The Ly-6G (Gr-1) positive neutrophils from CIA mice also expressed significant higher levels of adhesion molecule, integrin subunit CD11b (Mac-1α) . The number of CD19 positive (B) cells was increased. The percentage and number of CD3 positive (T) cells and the distribution of T cell subpopulations (CD4, CD8) were significantly increased. And the increase in CD4/CD8 was observed. From the results of day 42, we found that these responses on leukocytes gradually returned to the intact levels by day 42. These findings indicate that neutrophils considered to contribute to host defense also play an important function in modulating the development of inflammatory-immune response; CIA. The CIA induced increment of CD4 positive cells which was more predominant than that of CD8. [Jpn J Physiol 54 Suppl:S247 (2004)]

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We examined doses and time of administration of lipopolysaccharide (LPS) which activates innate immunity via the Toll-like receptor 4. It has also been considered that LPS modifies the adaptive immunity response on mouse collagen-induced arthritis (CIA). DBA/1J male mice were immunized 200 μg of bovine type II collagen emulsified in CFA and boosted 21 days later. A single i.p. injection of LPS at doses of 4 or 40 μg/body was delivered on day 28. Freshly isolated peripheral leukocytes from intact, CIA, and CIA-LPS mice on day 35 and 42 were stained with mAbs and counted by FACSCalibur (BD Biosciences). The severity of visual scoring of CIA-LPS was slightly higher than that of CIA. On day 35, compared with CIA, CIA-LPS did not show the leukocyte number increment, and the proportion of granulocyte/lymphocyte increased. The percentage and number of CD11b/Ly6G positive neutrophils increased as same level as those in CIA. The number of CD19 positive (B) cells and CD3 positive (T) cells were significantly decreased. Among T cell subpopulations, the percentage of CD4 positive cells was significantly decreased. As to a dose, 4μg/body administrated mice showed the decrease on visual scoring variability within experiments. At a dose of 40 μg/body, the exacerbation of body condition including body weight loss was marked. These findings indicate that the relative increase of granulocyte percentage might be an essential factor that exacerbates joint inflammation, and the administration of 4 μg/body will be recommended to enhance CIA. [Jpn J Physiol 54 Suppl:S248 (2004)]

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Lipopolysaccride (LPS) induces the production and release of inflammatory mediators, and elicits the activity of hypothalamus-pituitary-adrenal (HPA) axis. The activation of HPA axis can be potentiated by central PGs and NE released from adrenergic terminals projected from the brain stem, and inhibited by central nitric oxide (NO). The potential interaction between PGs, NE and the one NO is not clear. In order to explore the potential role of PGs and NE in the activities of neurons containing NOS, we investigated the effect of indomethacin and prazosin on the activation of neurons containing NOS induced by LPS with the method of combined Fos immunohistochemistry stain with NADPH stain (the marker of NOS). Our results showed that the NADPH positive neurons are mainly restricted in the PVN and SON. LPS (i.v) significantly induced the Fos expression in the NADPH positive neurons in the nucleus while little Fos expression can be detected in the NADPH positive neurons in the vehicle-treated animals. Pretreatment of indomethacin (i.v), or prazosin (i.v) dramatically suppressed the Fos expression in the NADPH positive neurons challenged by LPS. Our results suggest that in the inflammatory stress, central excitatory neurotransmitters of HPA axis, PGs and NE, can effectively mediate the activation of neurons containing NOS in the PVN and SON. Furthermore, NE can exert its effect on activation of the neurons containing NOS through the α-adrenoceptor. [Jpn J Physiol 54 Suppl:S248 (2004)]

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We investigated the mechanisms underlying regulation of contraction with measurements of isometric force and intracellular calcium concentration ([Ca²⁺] _i) in NIH 3T3 fibroblast re-constituted into fibers using a collagen matrix. Treatment with the major phospholipids, neurotransmitters and growth factors had little effect on baseline isometric force. However, U46619, a thromboxane A₂ (TXA₂) analogue, increased force and [Ca²⁺] _i. The time courses were similar to those induced by calf serum (CS) and the maximal force was 65% of a CS-mediated contraction. The selective TXA₂ receptor antagonist, SQ29548, abolished the U46619-induced responses. CS-induced contractions are dependent on an intracellular calcium store function; however, the U46619 response depended not only on intracellular calcium stores but also calcium influx from the extracellular medium. Inhibition of Rho kinase suppressed both U46619- and CS-induced responses; in contrast, inhibition of protein kinase C (PKC) reduced only the U46619 response. Moreover, addition of U46619 to a CS contracture enhanced force and [Ca²⁺] _i responses. These results indicate that U46619-induced responses involve both PKC and Rho kinase pathways, in contrast to activation by CS. TXA₂ thus may have a role in not only the initial step of wound repair as an activator of blood coagulation, but also in fibroblast contractility in later stages. [Jpn J Physiol 54 Suppl:S248 (2004)]

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