Cocaine disrupts estrous cyclicity and alters the reproductive neuroendocrine axis in the rat

Although a common drug of abuse, cocaine’s effects on cyclic reproductive functions and the neuroendocrine systems regulating these functions have not been studied. Here, we report the effects of cocaine on (1) estrous cyclicity and ovulation rates and (2) the stimulated in vitro release of hypothalamic GnRH and aminergic neurotransmitters directly involved in regulating or modulating GnRH release. Within 7 days of treatment with 10 mg kg^-1 day^-1 of cocaine HC1 subcutaneously, rats demonstrated significant estrous cycle irregularity including repetitive days of estrus and prolonged periods of diestrus. After 6 weeks of treatment, cocaine-treated rats exhibited a 44.3% decrease in ovulation rates. For the in vitro studies, bilaterally ovariectomized rats were injected with cocaine (10 mg kg^-1 day^-1) or with saline for 2 weeks. Each rat received estradiol benzoate (50 mg kg^-1 day^-1 s.c.) for 2 days before sacrifice. Hypothalamic slices were prepared, placed in 0.1 ml microchambers and perfused with modified Krebs buffer (pH 7.4) using a programmable perfusion system. Basal release of norepinephrine (NE) and serotonin (5HT) was significantly increased in the cocaine-treated group versus controls. Ten-minute pulses of 10^-7M progesterone (P₄) increase NE and 5HT, but not dopamine (DA), release in the saline-treated group. In contrast, pulses of P₄ increased NE, but not 5HT or DA, in the cocaine-treated rats. Ten-minute pulses of 0.1 mM NE increased GnRH release in both saline- and cocaine-treated rats. However, the response to pulsed NE was significantly attenuated in the cocaine-treated group. The results of this study demonstrate that cocaine disrupts estrous cyclicity by altering the hypothalamic amine activity necessary for pulsatile hypothalamic GnRH release. However, a direct effect of cocaine on the pituitary gland or ovaries cannot be excluded on the basis of these results.