| Co-Investigator(Kenkyū-buntansha) |
FURUKAWA Yasuo Hiroshima University, Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (40209169)
TAKASE Minoru Hiroshima University, Graduate School of Science, Research Associate, 大学院・理学研究科, 助手 (80226779)
UKENA Kazuyoshi Hiroshima University, Faculty of Integrated Arts and Sciences, Graduate School of Biosphere Science, Research Associate, 総合科学部, 助手 (10304370)
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| Research Abstract |
Peripheral steroid hormones act on brain tissues through intracellular receptor-mediated mechanisms to regulate several important brain neuronal functions. Therefore, the brain is considered to be a target site of steroid hormones. However, it is now established that the brain itself also synthesizes steroids de novo from cholesterol. The pioneering discovery of Baulieu and his colleagues, using mammals, and our studies with nonmammals have opened the door of a new research field. Such steroids synthesized in the brain are called neurosteroids.
To analyze neurosteroid actions in the regulation of motivation of instinct behaviors, we need data on the specific synthesis of neurosteroids in particular sites of the brain at particular times. Such informations are essential to develop hypotheses predicting the potential roles of particular neurosteroids. We therefore demonstrated the specific synthesis of neurosteroids, such as pregnenolone, pregnenolone sulfate, progesterone and its metabolite, in the hypothalamic and preoptic neurons, which are known to play an important role in the process of motivation of instinct behaviors. Interestingly, the biosynthesis of neurosteroids in these neurons increased during breeding season when reproductive instinct behaviors become actively in wild vertebrates.
Finally, we investigated the action of neurosteroids produced in the hypothalamic and preoptic areas using wild vertebrates. Our studies indicated that pregnenolone sulfate, progesterone and progesterone metabolite act on preoptic neurons to regulate the process of motivation by nongenomic mechanisms.
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