Chikara Hirono

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Receptors for excitatory amino acids in the mammalian central nervous system are classified into three major subtypes, ones which prefer N-methyl-D-aspartate (NMDA), quisqualate (QA), or kainate (KA) as type agonists respectively. These receptors are considered to mediate fast postsynaptic potentials by activating ion channels directly (ionotropic type).(More)
Microinjection of mRNA from adult rat brains into Xenopus oocytes induced an electrophysiological response to acetylcholine in the cells. The cells responded to acetylcholine through muscarinic receptors which appeared on the cell surface after microinjection of the mRNA and showed the depolarization, mainly due to an increase in membrane permeability to Cl(More)
Microinjection of rat brain mRNA in Xenopus oocytes induced acetylcholine, neurotensin, serotonin, and glutamate receptors in the cells. These receptors stimulate an intracellular reaction pathway, including G-protein activation, inositol trisphosphate (IP3) formation, and Ca2+-dependent Cl- channels. In the present study, we examined the roles of several(More)
Isoproterenol (IPR) and 8-(4-chlorophenylthio)-cyclic AMP (cpt-cAMP) enhanced carbachol (CCh)-induced fluid secretion from rat parotid glands, but had no effect by themselves. The enhancement by IPR was blocked by propranolol. In dispersed parotid acinar cells, IPR and cpt-cAMP potentiated CCh-induced K+ and Cl- currents (IK and ICl). IPR at the(More)
Xenopus oocytes in which poly(A)+ mRNA isolated from rat brains were previously injected, exhibited at least 3 categories of current responses to excitatory amino acids. They were oscillatory responses to glutamate (Glu) or quisqualate (QA), smooth large responses to kainate (KA), and smooth small responses to Glu and QA. Oscillatory responses were mediated(More)
Elevations of cytoplasmic free calcium concentrations ([Ca(2+)](i)) evoked by cholinergic agonists stimulate isotonic fluid secretion in salivary acinar cells. This process is driven by the apical exit of Cl(-) through Ca(2+)-activated Cl(-) channels, while Cl(-) enters the cytoplasm against its electrochemical gradient via a loop diuretic-sensitive(More)
1. The intracellular reaction mechanism underlying electrophysiological responses evoked by neurotensin (NT) was studied using Xenopus laevis oocytes injected with poly (A)+ messenger ribonucleic acid (mRNA) isolated from rat brains. 2. A few days after the injection of mRNA, oocytes were found to acquire sensitivity to NT and substance P. 3. Under(More)
The effects of muscarinic and beta-adrenergic agonists on Cl(-) currents in acinar cells were investigated to clarify their role in the regulation of fluid secretion in rat perfused submandibular glands. Additions of isoproterenol (IPR) at 10(-8) to 10(-6) M and 8-(4-chlorophenylthio)-cyclic AMP (CPT-cAMP) at 10(-3) M to the perfusate suppressed carbachol(More)
Effects of cytochalasin D on actin filaments in cells encircling taste pores were examined to clarify the functional role of actin filaments in the maintenance of taste pores in rat fungiform papillae, using a confocal laser microscope and a scanning electron microscope. Fluorescence in the taste pore cells was detected as a ring shape produced by actin(More)
Mastication and swallowing increase the heart rate, and posture change and respiration also modulate the heart rate. To clarify the role of mastication and swallowing in the modulation of the autonomic nervous activity, we investigated how they interact with modulation of the heart rate by changing body positions and respiration in young healthy subjects.(More)