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 admi nistration on pituitary gonadotrophin secretion in adult female rats. Ovari ectomized, oestradiol-treated rats were infused i.v. with 0.1 ml normal sal ine or 2 mg cocaine hydrochloride kg(-1). Blood samples were collected imme diately before cocaine infusion and at 3, 10, 30 and 60 min after cocaine i nfusion. Circulating LH concentrations were increased by 10 min after cocai ne administration (P < 0.05 versus saline-treated controls) and decreased t hereafter. Serum FSH concentrations were not significantly different from t hose of saline-infused controls at any time. In a second experiment, oestra diol-treated, ovariectomized rats were infused i.v. with: saline only, 2 mg cocaine hydrochloride kg(-1) in saline, 200 ng synthetic GnRH in 100 pl PB S or 200 ng synthetic GnRH plus 2 mg cocaine hydrochloride kg(-1) in PBS. B lood samples were collected immediately before drug infusions and 20 min la ter. Cocaine had no effect on either GnRH-stimulated LH or FSH secretion. I n a third experiment, pituitary cells were obtained from oestradiol-treated , ovariectomized rats. The cell cultures were exposed to 25 ng cocaine hydr ochloride ml(-1), 10(-10)-10(-7) mol GnRH l(-1) with and without 25 ng coca ine 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-s timulated LH or FSH secretion from pituitary cells in vitro. On the basis o f these results it is suggested that acutely administered cocaine stimulate s release of hypothalamic GnRH, which, in turn, stimulates pituitary gonado trophin secretion. Acute administration of cocaine does not appear to affec t pituitary gonadotrophin secretion directly.