title: Serotonin levels in the dorsal raphe nuclei of both chipmunks and mice are enhanced by long photoperiod, but brain dopamine level response to photoperiod is species-specific.
abstract: Seasonal affective disorder (SAD) is a subtype of major depressive or bipolar disorders associated with the shortened photoperiod in winter. This depressive disorder is integrally tied to the seasonal regulation of the brain's serotonergic system. Recently, we found that C57BL/6J mice subjected to a forced-swim test exhibited immobility, a photoperiod-dependent depression-associated behavior, and suppression of brain serotonin levels. However, mice are nocturnal animals, and it is unclear whether the brain serotonergic system responds similarly to photoperiod in nocturnal and diurnal species. This study compared the responses of brain serotonergic and dopaminergic systems to photoperiod in diurnal chipmunks and nocturnal C57BL/6J mice. In both species, serotonin levels in the dorsal raphe nuclei were higher under long-day conditions than short-day conditions, suggesting a similarity in the photoperiod responses of the serotonergic systems. However, photoperiod affected dopamine levels in various brain regions differently in the two species. Some chipmunk brain regions exhibited stronger photoperiod-induced changes in dopamine levels than those of C57BL/6J mice, and the direction of the changes in the hypothalamus was opposite. In conclusion, photoperiod may regulate the brain serotonergic system through similar mechanisms, regardless of whether the animals are diurnal or nocturnal, but photoperiod-dependent regulation of brain dopamine is species-specific.
authors: Laboratory of Regulation in Metabolism and Behavior, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
authors: Ryosei
authors: R
authors: Goda
authors: Laboratory of Regulation in Metabolism and Behavior, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
authors: Tsuyoshi
authors: T
authors: Otsuka
authors: Laboratory of Regulation in Metabolism and Behavior, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
authors: Ayaka
authors: A
authors: Iwamoto
authors: Laboratory of Regulation in Metabolism and Behavior, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
authors: Misato
authors: M
authors: Kawai
authors: Laboratory of Regulation in Metabolism and Behavior, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
authors: Satomi
authors: S
authors: Shibata
authors: Laboratory of Regulation in Metabolism and Behavior, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
authors: Mitsuhiro
authors: M
authors: Furuse
authors: Laboratory of Regulation in Metabolism and Behavior, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: syasuo@brs.kyushu-u.ac.jp.
authors: Shinobu
authors: S
authors: Yasuo
mesh_terms: D000818:Animals; D001831:Body Temperature; D002940:Circadian Rhythm; D004298:Dopamine / Q000378:metabolism*; D065847:Dorsal Raphe Nucleus / Q000378:metabolism*; D008297:Male; D008810:Mice, Inbred C57BL; D017440:Photoperiod; D012589:Sciuridae; D012701:Serotonin / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D012701:Serotonin; D004298:Dopamine
keywords: Chipmunk; Dopamine; Photoperiod; Raphe nuclei; Seasonal affective disorder; Serotonin