EFFECTS OF DOPAMINE D1 AND D2 RECEPTOR AGONISTS AND ANTAGONISTS ON BASAL AND ETHANOL-MODULATED BETA-ENDORPHIN SECRETION FROM HYPOTHALAMIC NEURONS IN PRIMARY CULTURES

In the present study, we determined the effects of dopamine receptor a gonists and antagonists on basal and ethanol-modulated beta-endorphin (beta-EP) secretion from hypothalamic neurons in primary cultures. Tre atment with various concentrations of dopamine DI agonist SKF 38393 an d D1 antagonist SCH 23390 did not affect basal IR-beta-EP release. How ever, dopamine D2 receptor agonist LY 141865 reduced basal immunoreact ive (IR)-beta-EP release in a concentration dependent manner. D2 recep tor antagonist, sulpiride, on the other hand, stimulated basal IR-beta -EP release and blocked LY 141865-induced inhibition of IR-beta-EP rel ease in a concentration dependent manner. When the actions of these DA receptor agents on ethanol-modulated IR-beta-EP release were studied, both D1 and D2 receptor agents failed to affect ethanol-modulated IR- beta-EP release. These data suggest that the endogenous secretion of b eta-EP from hypothalamic neurons is under the influence of an inhibito ry dopaminergic system involving the D2 receptor. Furthermore, ethanol 's effects on beta-EP secretion are not mediated by dopamine.