K-I Shimamura

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Sympathoadrenal medullary functions were investigated in stroke-prone spontaneously hypertensive rats (SHR-SP) and in control normotensive Wistar-Kyoto rats (WKY) under halothane-anesthetized and resting conditions. The mean frequency of the spontaneous efferent activity of a single adrenal sympathetic nerve fiber was 1.08 +/- 0.11 impulses/s in WKY and(More)
The non-competitive N-methyl-D-aspartate NMDA receptor antagonist ketamine, a dissociative anesthetic capable of inducing analgesia, is known to have psychotomimetic actions, but the detailed mechanisms remain unclear because of its complex properties. The present study elucidated neural mechanisms of the effect of ketamine, at doses that exert(More)
Traumatic events during early life may affect the neural systems associated with memory function, including extinction, and lead to altered sensitivity to stress later in life. We recently reported that changes in prefrontal synaptic efficacy in response to extinction trials did not occur in adult rats exposed to early postnatal stress (i.e. footshock [FS](More)
Two kinds of outward K+ currents were examined in single smooth muscle cells from pregnant rat uterus, using whole-cell voltage clamp. The first and faster component was more sensitive to 4-aminopyridine (4-AP), whereas the second and slower (delayed) component was more sensitive to tetraethylammonium (TEA). A possible third K+ component (Ca activated K+(More)
Single units of the adrenal sympathetic nerve (n = 46) were dissected and characterized with respect to tonic discharge and response to cutaneous and baroreceptor stimulation. The frequency of tonic discharge averaged 1.6 Hz and cardiovascular rhythmic modulation was observed in 53% of the units. The stimuli employed in the present study included(More)
The effects of oxytocin, a uterotonic polypeptide hormone, on the voltage-dependent slow calcium, fast sodium, and potassium channel currents were studied using whole-cell voltage clamp of freshly isolated cells from late pregnant (18-21 day) rat myometrium. The calcium current was rapidly inhibited by oxytocin (about 25% inhibition at 20 nM) in a(More)
The effects of oxytocin (OT) on holding current were studied in uterine smooth muscle cells freshly isolated from the longitudinal layer of 18-20 day pregnant rats, using the nystatin method of whole-cell voltage clamp. As we previously reported, the voltage-dependent Ca2+ current (L type) was partially inhibited by OT (about 30% inhibition at 1 microM).(More)
In precontracted, endothelium-free guinea pig mesenteric artery rings, in which adrenergic vasoconstrictor responses had been eliminated, guanethidine (1-30 microM) produced a vasodilatation of 69.3+/-4.4%. The vasodilatation was reduced 89% by capsaicin (10 microM) or 55% by tetrodotoxin (10 microM), indicating mediation of this effect by primary sensory(More)
Daily administration of clonidine for 5 weeks (approx. 300 micrograms/kg/day, p.o.) produced significant decreases in blood pressure and renal sympathetic efferent activity in spontaneously hypertensive rats (SHR). After cessation of clonidine administration, blood pressure and sympathetic nerve activity recovered rapidly from the depressed levels to the(More)