title: Changes in vasoactive intestinal peptide mRNA levels in the rat suprachiasmatic nucleus following p-chlorophenylalanine (PCPA) treatment under light/dark conditions.
abstract: Photic stimulus and serotonin (5-hydroxytryptamine; 5-HT) are two factors known to regulate vasoactive intestinal peptide (VIP) synthesis in the suprachiasmatic nucleus (SCN). To explore the role of 5-HT in the photic stimulus-induced change in VIP synthesis, we investigated the changes in level of VIP mRNA under a 12 h light/12 h dark cycle following depletion of 5-HT by intraperitoneal administration of p-chlorophenylalanine (PCPA) methyl ester (200 mg/kg concentration) for 3 successive days. To estimate VIP mRNA expression, we performed in situ hybridization using imaging plates combined with microcomputer-based imaging analysis. In light-phase, total signals of VIP mRNA from the PCPA-treated rats showed a significant decrease compared with those from the saline-treated control rats. However, in dark-phase, there were no significant decreases between the PCPA-treated rats and the saline-control rats. The present results strongly suggest that 5-HT neuronal inputs to the SCN interfere with the effect of photic stimulus on VIP synthesis at the mRNA level.
authors.affiliation: Department of Psychiatry, Kyoto Prefectural University of Medicine, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Kawakami
authors.forename: H
authors.initials: H
authors.lastname: Okamura
authors.forename: Y
authors.initials: Y
authors.lastname: Tamada
authors.forename: T
authors.initials: T
authors.lastname: Nakajima
authors.forename: Y
authors.initials: Y
authors.lastname: Ibata
mesh_terms: D000818:Animals; D003624:Darkness; D010134:Fenclonine / Q000494:pharmacology*; D017403:In Situ Hybridization; D008027:Light; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D018490:Serotonin Agents / Q000494:pharmacology*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D014660:Vasoactive Intestinal Peptide / Q000096:biosynthesis*
chemical_list: D012333:RNA, Messenger; D018490:Serotonin Agents; D014660:Vasoactive Intestinal Peptide; D010134:Fenclonine