Role of Endogenous Glutaminergic Systems in Mammalian Pineal Gland : A novel inhibitory systems for melatonin synthesis.

点击翻译按钮获取中文摘要

Mammalian pinealocytes synthesize and secrete melatonin, a hydrophobic hormone that affects many physiological functions such as circadian rhythm and seasonal reproduction.Besides melatonin, pinealocytes have been found to secrete L-glutamate by exocytic mechanism : pinealocytes accumulate L-glutamate in microvesicles (MVs) and secrete it through Ca2+ regulated exocytosis.Previously we showed that this system functions as a negative regulatatory mechanism for melatonin synthesis.In this project, we characterized in somje details on the endogenous glutaminergic systems and obtained following results.(1) Metabotropic glutamate receptor type 3 (mGluR3) is involved in the systems through an inhibitory G proteins-mediated signaling cascade.(2) Acetylcholine triggers glutamate exocytosis via nicotinic acetylcholine receptor in rat pinealocytes.(3) MVs contain some synaptic vesicle marker proteins such as SV2B, confirming MVs as counterparts of neuronal synaptic vesicles.(4) Pinealocytes contain high concentration of D-aspartate, which may also function as an inhibitory transmitters.(5) GluR1, an isoform of AMPA-type iGluRs, is predominantly expressed and functions in pinealocytes.