Effect of voltage-dependent calcium channel blockers on ethanol-induced beta-endorphin release from hypothalamic neurons in primary cultures

The voltage-dependent calcium channel (VDCC) has been shown to mediate calc ium entry into neurons that regulates neurotransmission in many neuronal ce lls. Four major types of VDCCs (three high-voltage-activated L-, N-, and P- types and one low-voltage-activated T-type) have been identified in neurons . Involvement of the VDCC in ethanol-stimulated beta-endorphin (beta-EP) re lease from hypothalamic neurons has not been studied. In the present study, the role of VDCC on basal and ethanol-induced beta-EP release was determin ed by using rat fetal hypothalamic cells in primary cultures. Treatments wi th a 50 mM dose of ethanol for 3 hr increased immunoreactive beta-EP (IR-be ta-EP) release from hypothalamic cells maintained in cultures for 9 days. E thanol-induced IR-beta-EP release was inhibited by a P/Q-type channel block er omega-agatoxin TK (0.1-1 mu M), an N-type channel blocker omega-conotoxi n (0.1-1 mu M), an L-type blocker nifedipine (1-10 mu M), and a T-type bloc ker flunarizine (1-10 mu M) The minimal effective doses of these blockers t hat blocked the ethanol response produced no significant effects on basal r elease of IR-beta-EP; neither did these doses of the blockers produce any s ignificant effects on cell viability. These results suggest that ethanol-st imulated IR-beta-EP release is regulated by extracellular calcium involving P-, N-, L- and T-type channels.