CYCLIC-AMP AND ETHANOL INTERACT TO CONTROL APOPTOSIS AND DIFFERENTIATION IN HYPOTHALAMIC BETA-ENDORPHIN NEURONS

In this study we have determined the role of cyclic AMP on the functio n and differentiation of beta-endorphin (beta-EP) neurons in rat fetal hypothalamic cell cultures. Addition of Bt(2)cAMP or the cAMP elevati ng agent, forskolin, in cultures, dose and time dependently increased beta-endorphin secretion. The increased beta-EP secretion after Bt(2)c AMP or forskolin treatment was associated with proopiomelanocortin gen e expression, enhanced neurite growth, and increased neuronal viabilit y. Determination of internucleosomal cleavage of DNA by agarose gel el ectrophoresis revealed that apoptosis occurred in hypothalamic neurons during the first 6-8 days in culture. Addition of Bt(2)cAMP during th is developmental period inhibited DNA degradation in hypothalamic neur ons. Furthermore, incubation with various doses of ethanol, which is k nown to reduce intracellular levels of Bt(2)cAMP, increased DNA degrad ation in these cells. Ethanol-induced DNA degradation was blocked by c oncomitant incubation with Bt(2)cAMP. Histochemical identification of apoptotic cells following ethanol and Bt(2)cAMP treatments further rev ealed that apoptosis occurred in beta-EP neurons during the developmen tal period, and that ethanol increased and Bt(2)cAMP reduced apoptotic beta-EP cell numbers. These results suggest that ethanol neurotoxicit y on beta-EP neurons during early neuronal differentiation involves an apoptotic process and that the cAMP signaling system plays an importa nt role in controlling apoptosis and differentiation of the beta-EP ne uronal system.