Luteinizing hormone-releasing hormone (LHRH) biosynthesis and secretion inembryonic LHRH neurons

Evidence indicates that LH-releasing hormone (LHRH) neurons can exhibit neu roendocrine secretory properties before entrance into the central nervous s ystem. In this study, we evaluated LHRH biosynthesis and secretion in embry onic LHRH neurons maintained in nasal explants. Using ELISA and calcium ima ging techniques, peptide content and single neuron activities mere examined . LHRH neurons maintained for 7-10 days in vitro mere found to possess a si milar amount of LHRH/cell as the equivalent aged LHRH cells in vivo (postna tal day ). LHRH peptide was measured in the medium of these relatively youn g cultures, and 40 mM KCl stimulated a 4-fold increase in LHRH secretion. K CI enhanced medium also resulted in a significant increase in LHRH content per culture (24.5 pg vs. 32.3). A similar effect was observed after muscimo l-enhanced media (32.2 pg). Both agents also stimulated a substantial rise in intracellular calcium. Pretreatment of cultures with tetrodotoxin partia lly blacked the affects of muscimol on both peptide content and calcium act ivity, but not KCl. Calcium-depleted medium blacked the effects of KCl yet only attenuated the effects of muscimol. Treatment of cultures with cyclohe ximide blocked the effects of both muscimol and KCI. These results indicate that developing LHRH neurons are capable of synthesizing, secreting, and r apidly replenishing stores of LHRH peptide.