| Co-Investigator(Kenkyū-buntansha) |
WAKISAKA Satoshi Osaka University, Department of Oral Anatomy, Associate Professor, 歯学部, 助教授 (40158598)
MATSUO Ryuji Osaka University, Department of Oral Physiology, Associate Professor, 歯学部, 助教授 (30157268)
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| Research Abstract |
Immunohistochemical studies were performed to exmine the location of c-fos expression in the rat brainstem to stimulation including gustatory, oral tactile, oral temperature, and bodily somatic sensory, and visceral (intraperitoneal injection of LiCl or intragastric infusion of various taste solutions) stimulation. Among these stimulation, gustatory and visceral stimuli induced the most dominant c-fos expression. That is, strong c-fos exprssion was observed in the area postrema and caudal part of the nucleus tractus solitarius (NTS), and the parabrachial nucleus (PBN) in response to gustatory and visceral stimulation. Since a chemotopic organization was detected in the PBN,c-fos expression in the PBN was surveyed precisely, i.e., the distribution of evoked expression of c-fos was immuno-histochemically examined in the PBN of water-deprived rats after free ingestion of palatable liquids, after intra-oral infusion of aversive taste solutions including various bitter substances, and after an intraperitoneal injection of LiCl. C-fos immunoreactive neurons (c-fos neurons) were densely packed in the external lateral subnucleus (els), external medial subnucleus (ems), dorsal lateral subnucleus (dls), central lateral subnucleus (cls), and the central medial subnucleus (cms) dcpcnding on the kind of stimulation. The rostral part of the cls may be related to general visceral inputs ; the caudal part of the els, negative hedonics or aversive bchavior ; the dls, positive hedonice or ingestive behavior. Both the ems and the els may be related to taste information for bitter tasting compounds and HCl ; the cls, for sucrose and saccharin ; and the ems, for NaCl. Such a chemotopic represention was similarly observed in rats with decerebration at the precollicular level, indicating that information processing in the PBN is performed mainly on the basis of peripheral inputs without involvement of the higher brain centers.
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