Effect of acute administration of cocaine on pituitary gonadotrophin secretion in female rats

The aim of this study was to characterize the acute effects of cocaine administration on pituitary gonadotrophin secretion in adult female rats. Ovariectomized, oestradiol-treated rats were infused i.v. with 0.1 ml normal saline or 2 mg cocaine hydrochloride kg^-1. Blood samples were collected immediately before cocaine infusion and at 3, 10, 30 and 60 min after cocaine infusion. Circulating LH concentrations were increased by 10 min after cocaine administration (P < 0.05 versus saline-treated controls) and decreased thereafter. Serum FSH concentrations were not significantly different from those of saline-infused controls at any time. In a second experiment, oestradiol-treated, ovariectomized rats were infused i.v. with: saline only, 2 mg cocaine hydrochloride kg^-1 in saline, 200 ng synthetic GnRH in 100 μl PBS or 200 ng synthetic GnRH plus 2 mg cocaine hydrochloride kg^-1 in PBS. Blood samples were collected immediately before drug infusions and 20 min later. Cocaine had no effect on either GnRH-stimulated LH or FSH secretion. In a third experiment, pituitary cells were obtained from oestradiol-treated, ovariectomized rats. The cell cultures were exposed to 25 ng cocaine hydrochloride ml^-1, 10^-10-10^-7 mol GnRH I^-1 with and without 25 ng cocaine hydrochloride ml^-1, or vehicle only. Medium was collected before and after exposure to GnRH to determine concentrations of secreted LH and FSH. Similar to the results of the second study, cocaine had no effect on GnRH-stimulated LH or FSH secretion from pituitary cells in vitro. On the basis of these results it is suggested that acutely administered cocaine stimulates release of hypothalamic GnRH, which, in turn, stimulates pituitary gonadotrophin secretion. Acute administration of cocaine does not appear to affect pituitary gonadotrophin secretion directly.