Auditory and vestibular inputs are applied to the hair cell hair bundle as mechanical energy, and are transduced into the electrical energy by gating ion channels, most likely at the base of the hair bundle. The mechano-electrical transduction channel has a unitary conductance of 50pS and has a broad selectivity to monovalent cations and to divalent cations. Ca ions are the most permeable through the channel. The angular displacement of the hair bundle is the primary gating factor. However, we still do not know the exact linkage between the angular displacement and the channel gating. Circumstantial evidence indicates a possibility of the direct gating of channels by the membran deformation itself. ATP and cholinergic muscarinic receptors likely mediate the inhibitory efferent innervation to the hair cell.

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Electrical activity was recorded intracellularly from the muscle cell of guinea-pig taenia caeci in Locke solution. Membrane potential was -46.4mV, and spike potentials were discharged spontaneously. Isoprenaline (3μM) hyperpolarized the membrane and suppressed the spike discharge. The hyperpolarization by isoprenaline was increased at low K (2mM), while decreased at high K (11.8, 29.5. 59mM). The hyperpolarization by isoprenaline was potentiated in the presence of external Mg ions, depending on the concentration of Mg (0-9.6mM). Forskolin (3μM) and papaverine (30μM) hyperpolarized the membrane; the effects were augmented by 1.2mM Mg. The hyperpolarization in response to 3μM isoprenaline or 100μM papaverine was inhibited by Mn, Co, and low Ca (1mM) whereas it was not affected by high Ca (7.5mM). Verapamil (0.5, 2μM) had no influence of the hyperpolarization caused by isoprenaline. It was discussed that extracellular and/or intracellular Mg and Ca ions played important roles in the β-adrenoceptor-mediated action on the smooth muscle membrane of taenia caeci.

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The loop gain (G) of the autonomic reflex function in orthostatic stress was assessed in anesthetized dogs subjected to 45 and 90° head-up tilt. We observed the magnitude of orthostatic hypotension before and after 1) sinus denervation and vagotomy (SDVT), or 2) ganglionic blockade (GB) with hexamethonium. The decreases in arterial pressure during the orthostatic stress before and after interruption of the autonomic reflex from either the afferent or efferent limb were defined as E and D, respectively. The loop G of the compensatory system was calculated using closed-loop analysis: G=(D/E)-1. In the SDVT experiments, the average values of E, D, and G were 18.6mmHg, 62.6mmHg, and 2.36, respectively for 45° tilt; and 31.2mmHg, 82.7mmHg, and 1.63, respectively for 90° tilt. In the GB experiment, the E, D, and G values were 14.6mmHg, 51.6mmHg and 2.53 for 45° tilt; and 28.9mmHg, 72.6mmHg, and 1.51 for 90° tilt. The data provide a quantitative measure of the autonomic reflex function in orthostatic hypotension. Furthermore, we found that the corresponding G values in the SDVT and GB experiments were not significantly different. In each experiment, the G value in 90° tilt was lower than that in 45° tilt. The findings suggest that reflexes from the arterial baroreceptors and cardiopulmonary receptors account for a large part of the autonomic compensation to the orthostatic stress. The whole control system operates in a nonlinear fashion, because the gain value tends to decrease as the degree of tilt is increased.

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The concentration of cytosolic Ca²⁺ ([Ca]_in) was examined in single bovine adrenal chromafhin cells by monitoring fura-2 fluoresence with microspectrofluorimetry. To see the correlation between [Ca]_in and secretion, we also measured the rates of catecholamine (CA) secretion and ⁴⁵Ca efflux from populations of cells. [Ca]_in was constant in the majority of single cells, but the small oscillatory changes in [Ca]_in were observed in a population of cells. These spontaneous Ca oscillations, when observed, disappeared either after removal of extracellular Ca²⁺ or by addition of D-600 or Mn²⁺, but still persisted in the presence of tetrodotoxin (TTX) or after removal of extracellular Na⁺. In the silent cells the Ca fluctuations were often induced by Bay-K-8644. The characteristics of Bay-K-8644-induced Ca fluctuations were very similar to those of spontaneous ones. Low concentrations of nicotine (1μM), acetylcholine (ACh; 1-2μM), or KCl (12.5mM) often induced oscillations riding on a steady rise in [Ca]_in. These changes were rapidly suppressed by removal of either extracellular Ca²⁺ or Na⁺, or by addition of either D-600 (methoxyverapmil) or TTX. A low concentration of ACh (1μM) or KCl (12.5mM) also increased the rate of ⁴⁵Ca efflux, but substantial secretion was not detected. On the other hand, the sustained rise in [Ca]_in was evoked by 0.1mM ACh, 20μM nicotine, or 30mM KCl, which was suppressed by removal of extracellular Ca²⁺, but was little affected by TTX. A sustained increase in ⁴⁵Ca efflux upon exposure to ACh was observed, possibly reflecting the sustained rise in [Ca]_in. ACh also stimulated CA secretion, which was faded out during the prolonged application. Veratridine, a Na channel activator, caused repetitive sequence of Ca transients followed by a sustained rise in [Ca]_in. These results, together with the previous electrophysiological findings, suggest that: (1) the spontaneous Ca fluctuations are closely associated with occurrence of spontaneous Ca²⁺ and Na⁺ action potentials; (2) the rise in [Ca]_in induced by a low concentration of nicotinic agonists of KCl is mediated by Na⁺ action potentials as well as gradual membrane depolarizations; (3) the oscillatory changes subsequent to a rise in [Ca]_in reflect fluctuations in Ca₂₊ influx through the Ca²⁺ channels; (4) the critical [Ca]_in needs to be attained before the CA secretion takes place.

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We studied the steady state responses of heart rate (HR) to carbon dioxide inhalation under hyperoxic, euoxic, and hypoxic conditions in 9 healthy men. With increasing end-tidal P_CO2, HR generally increased slightly. On the other hand, distinct increment in VE in response to step increase in end-tidal P_CO2 was observed in all three different conditions. Significant positive correlation between hypercapnic VE and HR responsiveness was found in both hyperoxic and hypoxic conditions, whereas no such tendency was seen in euoxic condition. We suggest that the effect of CO₂ inhalation on HR is mainly determined by the pulmonary inflation reflex in hyperoxia, the pulmonary inflation reflex plus peripheral chemoreceptor activity in euoxia, and the additional sympathetic and humoral factors in hypoxia, respectively.

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In groups of male Wistar rats, blood level, urinary excretion of urea, and renal urea clearance were determined in resting conditions or during 48-60h after swimming for 30min with an additional load of 10% of body weight as well as after swimming for 3 or 10h without additional load. Both types of swimming exercise caused a significant increase in the blood level, urinary excretion, and renal clearance of urea. After 10-h swimming, the increase of renal urea clearance was observed only from the second period (0-12h) of urine collection. In this type of exercise, an elevation of blood level of corticosterone was obtained after 6-h restitution. The increased urinary excretion and renal urea clearance persisted for a longer time than was necessary for the normalization of the blood level. A significant rise in blood urea level and a drop in renal urea clearance occurred after adrenalectomy. In adrenalectomized rats, increased urea excretion and renal clearance were observed 12-24h after 3-h swimming, but the level of renal clearance obtained in sedentary normal rats was not achieved. The blood level of urea did not increase. This suggested that the glucocorticoids play a role both in urea formation during exercise and in its elevated renal clearance after exercise.

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When a background light is delivered, the responsiveness of horizontal cells to light stimulus initially lowers but subsequently recovers gradually as shown by the increase in response amplitude to test light. These changes of responsiveness are observed when white or close wavelengths are used for both the background and test lights. However, the response amplitude to blue-green test light was initially enhanced but decreased and reached a steady state after the onset of red background illumination. The mechanism causing such a change of test responses was studied in the luminosity-type cone horizontal cells. The initial response enhancement was accompanied by an increase of the slope of hyperpolarizing phase, while the subsequent decrease of response amplitude was caused by the advancement of the recovery phase. The advancement of the recovery phase was eliminated by γ-aminobutyric acid (GABA) or Co²⁺ (50μM), which blocks GABA-induced currents in cone terminals. Dopamine, which inhibits GABA release from horizontal cells, stimulated the advancement of the recovery phase. The time course of the hyperpolarizing phase was not affected by these agents. The enhancement and the subsequent decrease of test responses were also observed in 6-hydroxydopamine-treated retinae. The results suggest that the GABAergic feedback pathway from horizontal cells to cones advances the recovery phase of response to test light. It appears, therefore, that the feedback modifies the responsiveness of horizontal cells to light stimulus under a red background illumination. The mechanism enhancing response amplitude will be also discussed.

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Cardiac sympathetic nerve activity (CSNA in imp/s) was measured in the postganglionic fibers of awake cats at rest, during body movement, and with excitement. The CSNA showed synchronized discharges with various periodicities. Rhythms of the synchronized CSNA were analyzed by an interval histogram (IIH). The IIH showed a multimodal distribution. The first model interval (T_c) was in a range of 75 to 125ms. An 8-12 cycle/s T_c rhythm, i.e., inverse value of T_c, was always observed in the awake cat at rest and during body movements. Probability of the 8-12 cycle/s T_c rhythm was smallest at rest, increased during body movement, and was largest with excitement. These results suggested that the 8-12 cycle/s T_c rhythm, observed in all states in the conscious cat, is a fundamental rhythm of central cardiovasomotor origin. The subsequent model distribution (T_b=2×T_c, 3×T_c, 4×T_c, or 5×T_c) ranged from 150 to 700ms, mostly 200 to 500ms. A 2-5 cycle/s T_b rhythm, i.e., inverse value of T_b, appeared more frequently at rest than that during body movement or with excitement. A new model concerning a mechanism to cause the 2-5 cycle/s T_b rhythm is suggested.

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When the finger is immersed in ice water, a sharp fall of the skin temperature is followed by its gradual rise due to the cold-induced vasodilatation (CIVD). The present study was attempted to examine whether the CIVD is affected by a small increase in internal heat load due to the dietary thermogenesis. A 10-min immersion of the left middle finger in ice water was performed at room temperature of 25-26°C on 12 female subjects 60min before, and 30 and 90min after ingestion of a meal containing 700kcal. Skin temperature of the finger and O₂ consumption were continuously measured before, during, and after the immersion. A CIVD index was measured using the data of the rising phase of skin temperature during the immersion. The CIVD index, a newly developed parameter in the present study, could reflect both the rapidity and the magnitude of CIVD response during the immersion. Compared with pre-prandial values, the O₂ consumption and the CIVD index significantly increased by 15 and 69%, respectively, at 30min and by 15 and 50% at 90min of the post-prandial period. Esophageal temperature was studied on another 5 subjects (1 male and 4 females) and it rose by 0.27°C during the 90-min post-prandial period. The results, in support of the involvement of the central nervous system control in CIVD, suggest that the central process is so sensitive as to operate in a 15% increase in heat load into the body.

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Relative ovarian weights with bursa and annual profiles of sex steroids have been described in the female musk shrew, Suncus murinus, collected in the vicinity of Rawalpindi, Pakistan. The relative gonadal wight was basal (23.20±1.20mg/100g) during anoestrus but enhanced (39.93±2.73mg/100g) abruptly at the onset of the breeding season. Plasma progesterone concentrations, measured during different parts of the year, indicated elevated levels during the late pregnant stage (p<0.01). The ovarian progesterone was also comparatively higher in late pregnant animals. No significant difference was observed in plasma and ovarian oestradiol.

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MC3T3-E1 osteogenic cells in a growing state were voltage-clamped by the whole-cell patch-clamp method. The MC3T3-E1 cells exhibited a transient, fast-inactivating Ca inward current upon depolarizing pulses from a holding potential of -80mV. This current had a threshold of activation of about -50mV and was insensitive to the dihydropyridine, nifedipine. These results show that MC3T3-E1 cells have a voltage-dependent Ca channel corresponding to the "T-type."

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A photoaffinity labeling technique was used to study the receptors involved in the discrimination of odorants. Aromatic azides, 1-azidonaphthalene (AzN) and 1-azido-4-nitronaphthalene (AsNN), were found to be pleasant-smelling compounds and produced good responses, giving standard EOG's (electro-olfactogram) of the kind observed for normal odorants. Following irradiation of the frog olfactory mucosa with light during constant stimulation with one of the azides vapor, there was a specific partial inhibition of the receptors for that odorant. The extent of reduction in amplitude of the EOG responses to AzN and AzNN varied between 40 to 60% of the original amplitude.

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