Cyclic AMP and ethanol interact to control apoptosis and differentiation in hypothalamic β-endorphin neurons

In this study we have determined the role of cyclic AMP on the function and differentiation of β-endorphin (β-EP) neurons in rat fetal hypothalamic cell cultures. Addition of Bt₂cAMP or the cAMP elevating agent, forskolin, in cultures, dose and time dependently increased β-endorphin secretion. The increased β-EP secretion after Bt₂cAMP or forskolin treatment was associated with proopiomelanocortin gene expression, enhanced neurite growth, and increased neuronal viability. Determination of internucleosomal cleavage of DNA by agarose gel electrophoresis revealed that apoptosis occurred in hypothalamic neurons during the first 6-8 days in culture. Addition of Bt₂cAMP during this developmental period inhibited DNA degradation in hypothalamic neurons. Furthermore, incubation with various doses of ethanol, which is known to reduce intracellular levels of Bt₂cAMP, increased DNA degradation in these cells. Ethanol-induced DNA degradation was blocked by concomitant incubation with Bt₂cAMP. Histochemical identification of apoptotic cells following ethanol and Bt₂cAMP treatments further revealed that apoptosis occurred in β-EP neurons during the developmental period, and that ethanol increased and Bt₂cAMP reduced apoptotic β-EP cell numbers. These results suggest that ethanol neurotoxicity on β-EP neurons during early neuronal differentiation involves an apoptotic process and that the cAMP signaling system plays an important role in controlling apoptosis and differentiation of the β-EP neuronal system.