Changes in vasoactive intestinal peptide mRNA levels in the rat suprachiasmatic nucleus following p-chlorophenylalanine (PCPA) treatment under light/dark conditions |
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| Authors: | Fumio Kawakami Hitoshi Okamura Yoshitaka Tamada Teruo Nakajima Yasuhiko Ibata |
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| Affiliation: | aDepartment of Psychiatry, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602, Japan;bDepartment of Anatomy, Kobe University School of Medicine, Kusunoki-cho, Chuo-ku, Kobe 650, Japan;cDepartment of Anatomy, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602, Japan |
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| 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 signifanct 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. |
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| Keywords: | Suprachiasmatic nucleus Vasoactive intestinal peptide Serotonin In situ hybridization p-Chlorophenylalanine |
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