Ascorbate-induced release of LHRH: noradrenergic and opioid modulation

Ascorbic acid caused a calcium-dependent release of luteinizing hormone-releasing hormone (LHRH) from the rat mediobasal hypothalamus in vitro. The ascorbate-induced release of LHRH was effectively blocked by the adrenergic alpha-receptor blocker phentolamine, but not by the beta-receptor blocker propranolol. The effect of ascorbate was also suppressed by the mu receptor selective opiate agonist sufentanil. These results suggest that the effects of ascorbic acid on the in vitro release of LHRH are mediated by endogenous norepinephrine. Moreover, our results are consistent with the hypothesis that the release of LHRH in the rat is regulated by the hypothalamic noradrenergic system, which is in turn modulated in some, as yet undetermined, fashion by opioid peptides.