Cocaine affects progesterone plasma levels in female rats

Female Fischer rats injected with cocaine in a "binge" pattern (15 mg/kg, I P, three times a day, at 1-h intervals) for 1 day had significantly higher levels of progesterone than saline-treated controls (p < 0.001). When analy zed by the stage of the estrous cycle, animals in proestrus showed signific antly higher cocaine-induced progesterone plasma levels than those in other stages of the cycle (p < 0.01). Progesterone plasma levels were also incre ased after a single dose of cocaine (15 mg/kg). However, 3 h postinjection progesterone plasma levels had returned to normal. Thus, cocaine modulation of progesterone plasma levels appears to be an acute effect. In ovariectom ized rats pretreated with estrogen, progesterone, or estrogen + progesteron e, no significant differences were observed in progesterone plasma levels a fter acute "binge" pattern cocaine administration. Thus, acute cocaine indu ced increases in progesterone plasma levels in intact female rats are proba bly due to an increase in secretion rates of progesterone rather than an ac celeration of its biotransformation. Due to the profound effects of progest erone in the modulation of CNS plasticity, the modulation of progesterone p lasma level by cocaine may have implications for reproductive processes and neuronal functions of women. Moreover, cocaine may affect the progesterone levels in women utilizing progesterone-based contraception or steroid repl acement treatment after menopause. (C) 2000 Elsevier Science Inc.