EFFECTS OF DOPAMINE ON PROLACTIN - INTERACTIONS WITH COCAINE SELF-ADMINISTRATION BY FEMALE RHESUS-MONKEYS

The effects of dopamine on regulation of prolactin secretion were stud ied in female rhesus monkeys before cocaine exposure and again after 2 months to 2.7 years of daily cocaine self-administration. During chro nic cocaine exposure, basal prolactin levels increased by 227 to 350% above drug-free control levels (P < .05). On each endocrine study day, three successive 80-min dopamine infusions (10 mu g/kg/min i.v.) were alternated with 20-min interruptions of dopamine infusions to assess the degree of prolactin suppression and the magnitude of postdopamine prolactin increases. Dopamine significantly reduced prolactin below ba se-line levels within 60 to 80 min under all conditions (P < .05-.01). In four drug-naive follicular phase females, postdopamine increases i n prolactin never exceeded predopamine base-line levels of 6.2 (+/-1.8 ) ng/ml. After an average of 74 days of cocaine self-administration [3 .7 (+/-0.11) mg/kg/day], the postdopamine prolactin increases were sig nificantly higher than during drug-free control conditions (P < .01) a nd reached hyperprolactinemic levels of 57.6 ng/ml. After an average o f 300 days of cocaine self-administration [6.5 (+/-0.06) mg/kg/day], p ostdopamine prolactin increases peaked at 339% above predopamine basal prolactin levels. After an average of 433 days of cocaine self-admini stration [6.45 (+/-0.08) mg/kg/day], postdopamine prolactin increases remained significantly higher (P < .01) than during drug-free conditio ns. A similar pattern of postdopamine prolactin increases to hyperprol actinemic levels (ranging from 44.5 to 141.2 ng/ml) also were measured in two other females studied after 19 to 20 months of cocaine self-ad ministration [6.21 (+/-0.11) and 7.49 (+/-0.17) mg/kg/day]. After 2.7 years of cocaine self-administration, one monkey developed persistent hyperprolactinemia and basal prolactin levels averaged 326 ng/ml after 89 days of cocaine abstinence. These data suggest that the prolactin secretory response to dopamine perturbation may provide a sensitive in dex of changes in dopaminergic regulation of prolactin during chronic cocaine exposure.