Elsevier

Neuroscience Letters

Volume 241, Issues 2–3, 30 January 1998, Pages 115-118
Neuroscience Letters

Pituitary adenylate cyclase-activating polypeptide rhythm in the rat pineal gland

https://doi.org/10.1016/S0304-3940(98)00041-XGet rights and content

Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP) was recently demonstrated to stimulate melatonin synthesis in the rat pineal gland. Circadian rhythms of melatonin concentration are well known. However, it has not been clarified whether PACAP contents in the pineal gland show circadian rhythm. In this study, we measured PACAP contents in the rat pineal gland throughout the day under 12:12 h light-dark cycle or constant dark conditions. A significant fluctuation was observed in the PACAP content under light-dark conditions but not under constant darkness. On the other hand, the pituitary gland showed no significant variation throughout the day under either conditions. These observations suggest that PACAP may participate in the modulation of melatonin synthesis depending on light conditions in the pineal gland.

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Acknowledgements

We would like to thank Drs. M. Takita, NIBH, Tsukuba and H. Okamura, Kobe University School of Medicine for their critical suggestion. C.F. was a recipient of JSPS Research Fellowships for Young Scientists. This work was supported by grants from the Ministry of Education, Science and Culture, Japan.

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