Abstract
In order to know whether or not the clock genes in the hippocampus are involved in prolonged hyperphagia produced by mild restraint, the expressions of clock genes, Per1 and Dec1, and Neuropeptide Y (NPY) gene in the rat hippocampus were examined by mean of in situ hybridization. Immediately after weaning, 6-8 female rats were restrained together in a small pouch for 30 min in the morning every second day for 4 weeks. Body weight as well as food and water intake were measured every day during and for 4 weeks after the stressor application. The rats were killed by decapitation 2, 4 and 6 weeks after weaning. The brain was frozen, cut in a frontal plane including the hippocampus and subjected to in situ hybridization. The hybridization signals were quantified by MCID. As a result, Per1 was expressed in all regions of the hippocampus, whereas Dec1 expression was restricted to CA1. NPY gene was expressed in CA1 and the dentate gyrus (DG). In the control rats, Per1 expression showed a significant day-night difference in DG, but not in other regions of the hippocampus. Restraint significantly increased Per1 expression in all regions of the hippocampus at 2, 4 and 6 weeks. On the other hand, Dec1 expression in CA1 was significantly suppressed by restraint during the entire period of experiment. Restraint has no effect on NPY expression in the hippocampus. These findings suggest possible roles of Per1 and Dec1 in the hippocampus in the stress response and/or prolonged hyperphagia. [Jpn J Physiol 54 Suppl:S207 (2004)]
