Progesterone and cocaine administration affect serotonin in the medial prefrontal cortex of ovariectomized rats

Due to the hypothetical role of ovarian hormones, estrogen and progesterone, in cocaine-induced behavioral activity and self-administration, this study investigated the effects of cocaine, estrogen, and progesterone administration on monoamine levels in the medial prefrontal cortex of ovariectomized hormone-treated rats. Rats were given either 'binge' cocaine or saline, and one of four hormone treatments: vehicle, estrogen, progesterone, or estrogen+progesterone. The co-administration of progesterone and cocaine resulted in increased levels of serotonin when compared to saline-treated controls and cocaine-treated animals in the other hormone-treatment groups. Further, progesterone-treated rats had higher levels of 5-HIAA than vehicle or estrogen-treated rats. Although levels of dopamine, DOPAC, and homovanillic acid were decreased after cocaine, these alterations failed to reach significance. These results show an interaction between the endocrine environment and cocaine-induced alterations in serotonin system in the medial prefrontal cortex. Thus, these changes may contribute to previously reported gender and estrous cycle differences in behavioral responses to cocaine.