Serotonin stimulates GnRH secretion through the c-Src-PLC gamma1 pathway in GT1-7 hypothalamic cells.

Serotonin is a neurotransmitter that alters the hypothalamic-pituitary-adrenal axis. To date, however, the molecular mechanisms underlying the role of serotonin in hormone secretion have remained largely unclear. In this study, we report that serotonin activates phospholipase C (PLC) gamma1 in an Src-dependent manner in hypothalamic GT1-7 cells, and that pretreatment with either 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazole [3, 4-d] pyrimidine, an Src-kinase inhibitor, or U73122, a PLC inhibitor, attenuates the serotonin-induced increase in calcium levels. Also, PLC gamma1 binds to c-Src through the Src-homology (SH) 223 domain upon serotonin treatment. Moreover, calcium increase is alleviated in the cells transientlyexpressing SH223 domain-deleted PLC gamma1 or lipase inactive mutant PLC gamma1, as compared with cells transfected with wild-type PLC gamma1. Furthermore, the inhibition of the activities of either PLC or Src results in a significant diminution of the serotonin-induced release of gonadotropin-releasing hormone (GnRH). In addition, the results of our small-interfering RNA experiment confirm that endogenous PLC gamma1 is a prerequisite for serotonin-mediated signaling pathways. Taken together, our findings demonstrate that serotonin stimulates the release of GnRH through the Src-PLC gamma1 pathway, via the modulation of intracellular calcium levels.