Changes in vasoactive intestinal peptide mRNA levels in the rat suprachiasmatic nucleus following p-chlorophenylalanine (PCPA) treatment under light/dark conditions.
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.
Kawakami
F
F
Department of Psychiatry, Kyoto Prefectural University of Medicine, Japan.
Okamura
H
H
Tamada
Y
Y
Nakajima
T
T
Ibata
Y
Y
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*
D012333:RNA, Messenger; D018490:Serotonin Agents; D014660:Vasoactive Intestinal Peptide; D010134:Fenclonine