The acute effects of i.v. cocaine on basal levels of prolactin (PRL), luteinizing hormone (LH) and follicle-stimulating hormone were examined in nine female rhesus monkeys during the early follicular phase of the menstrual cycle (days 4-7). Integrated plasma samples were collected at 10-min intervals for 40 min before and 110 min after administration of cocaine (0.4 and 0.8 mg/kg i.v.). Cocaine plasma levels averaged 105 +/- 19 and 157 +/- 23 ng/ml after low- and high-dose administration. PRL decreased significantly (P less than .01) after cocaine administration and reached a nadir within 60 to 70 min. Inasmuch as cocaine blocks dopamine reuptake, PRL suppression is consistent with dopaminergic inhibitory control of PRL release from the pituitary. However, cocaine's effects on PRL were biphasic in 10 of 18 studies. PRL increased within 90 to 110 min post-cocaine and sometimes exceeded base-line levels by over 100%. The duration of PRL suppression (80 min) and the time of onset of the subsequent rebound PRL increase corresponds to the estimated half-life of i.v. cocaine in monkey plasma. PRL suppression followed by a rebound elevation also is consistent with clinical reports of hyperprolactinemia in chronic cocaine abusers. LH increased significantly (P less than .01) within 20 min after cocaine administration and remained above base-line for 40 to 50 min. Follicle-stimulating hormone did not change significantly after cocaine administration. Cocaine's stimulation of LH is consistent with cocaine's alleged enhancement of sexual arousal.(ABSTRACT TRUNCATED AT 250 WORDS)