SCN Neurochemistry using In Vivo, Microdialysis in the Conscious Brain
Annual technical rept. 31 Dec 1992-31 Dec 1993
KENT STATE UNIV OH
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The central aim of this research is to provide information on the neurochemical processes that underlie the generation and entrainment of mammalian circadian rhythms. The studies are centered around the newly-developed in vivo brain microdialysis technique for assessing the daily patterns of neurotransmitter release in the suprachiasmatic nuclei SCN of freely-behaving hamsters. The expression of immediate early gene product, Fos, also was used to assess the function of cells in the SCN. During The last year this approach has yielded several new findings related to the activities of serotonergic and excitatory amino acid activities in the SCN. Specifically, it was found that 1 serotonin inhibits release of glutamate in the SCN via a 5-HTlA receptor 2 serotonin inhibits the signaling of photic information from the retina to the SCN, and this action is mediated probably via a 5-HT7 receptor mechanism 3 serotonin also inhibits electrical signaling from the retinohypothalamic tract to the SCN as well as light-induced phase shifts under free-running conditions many of these effects are mimicked by tryptophan loading, which is evidence that endogenous serotonin plays a physiological role in rhythm entrainment.
- Anatomy and Physiology