ACUTE EFFECTS OF COCAINE ON ANTERIOR-PITUITARY HORMONES IN MALE AND FEMALE RHESUS-MONKEYS

The effects of acute cocaine administration (0.4 or 0.8 mg/kg) on anterior pituitary hormones were studied in four male and six female adult rhesus monkeys during the midluteal phase of the menstrual cycle (days 20-23). Progesterone levels averaged 15.7 +/- 3 and 10.6 +/- 2.8 ng/ml before low and high dose cocaine administration. Integrated plasma samples were collected every 10 min for 40 min before i.v. administration of cocaine, and 11 postcocaine samples were collected over 110 min. Cocaine (0.8 mg/kg) stimulated a significant increase in luteinizing hormone (LH) within 10 to 20 min (P < .01) and LH reached peak levels (59-60% above base line) within 30 min after cocaine administration in both males and females. Plasma cocaine levels averaged 289 +/- 23 and 346 +/- 73 ng/ml at 10 min after i.v. cocaine (0.8 mg/kg) administration in males and females, respectively. Follicle stimulating hormone levels were unchanged in midluteal females. Male testosterone increased by 50% above average base-line levels 50 min after the LH peak (80 min postcocaine). These data are consistent with our previous findings that cocaine increased LH and enhanced luteinizing hormone-releasing hormone-stimulated LH in early follicular females. The low dose of cocaine did not change basal levels of LH and follicle stimulating hormone in midluteal females and both LH and testosterone were unaffected in males. Cocaine plasma levels averaged 97.6 +/- 29 and 68.3 +/- 9.1 ng/ml at 10 min after 0.4 mg/kg of cocaine in males and females, respectively. Prolactin levels decreased significantly in males within 40 min after 0.4 mg/kg cocaine administration and within 30 min after 0.8 mg/kg of cocaine administration (P < .05). Prolactin remained significantly below base-line levels (P < .05-.01) for 70 and 80 min after low- and high-dose cocaine administration, respectively, then began to increase 110 min after cocaine administration. In midluteal females, cocaine significantly decreased prolactin within 50 min (P < .05-.01) and this effect persisted for 50 min after 0.8 mg/kg of cocaine. These data suggest that cocaine's inhibition of dopamine reuptake down-regulates pituitary lactotroph activity in both male and female rhesus monkeys.