Takao Shimazoe (1), Miyuki Maetani (1), Sachiko Nakamura (1), Shiro Yamanouchi
(1), Shigenori Watanabe (1), Kyoko Miyasaka (2), Akira Kono (3) and Akihiro
(1) Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyushu University 62, Fukuoka 812-8582, Japan
(2) Department of Clinical Physiology, Tokyo Metropolitan Institute of Gerontology, Tokyo 173-0015, Japan
(3) National Kyushu Cancer Center, Fukuoka 811-1395, Japan
Abstract: The entrainment function in the suprachiasmatic nucleus (SCN) of young non-diabetic Otsuka Long Evans Tokushima Fatty (OLETF) rats was studied. OLETF rats significantly needed more days for re-entrainment to a new light-dark cycle than control Long Evans Tokushima Otsuka (LETO) rats. We also assessed Fos expression in the SCN induced by dim light exposure. The number of Fos-immuno-reactive cells was significantly decreased in 5- to 13-week-old OLETF rats compared with LETO rats. Moreover, the effect of glutamate on neuronal activity in the SCN of OLETF rats were investigated. In young non-diabetic OLETF rats, the phase delay in the SCN neuronal firing rhythm induced by 1 microM glutamate was significantly less than that in LETO rats. These results suggested that the entrainment function is reduced in OLETF rats before the onset of diabetes.
Keywords: Otsuka Long Evans Tokushima Fatty (OLETF) rat, Suprachiasmatic nucleus, Entrainment