Ethanol increases cholinergic and decreases GABAergic neuronal expression in cultures derived from 8-day-old chick embryo cerebral hemispheres: interaction of ethanol and growth factors.

We have shown that ethanol exposure during embryogenesis affects a variety of parameters of neuronal growth both in ovo and in vitro. Moreover, we have found that growth factors significantly attenuate the in ovo neurotoxicity produced by ethanol. In this study, we further examined the direct effects of ethanol exposure on neuron-enriched cultures derived from 8-day-old chick embryo cerebral hemispheres consisting primarily of differentiated neurons. In addition, we examined the interaction of ethanol and nerve growth factor (NGF) or epidermal growth factor (EGF) when the growth factors were given concomitantly with ethanol. Choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) were used as markers for cholinergic and GABAergic neuronal phenotypic expression, respectively. We found that ethanol alone enhanced ChAT and reduced GAD activities in a dose-dependent manner. NGF and EGF given alone enhanced the expression of both neuronal phenotypes. When NGF was given concomitantly with ethanol at C4-8 the decline in GAD produced by ethanol was reversed. The effects of concomitant administration of ethanol and growth factors on ChAT activity revealed that ethanol interfered with the increases produced by the growth factors and especially with NGF when given alone. We conclude from these findings that ethanol may interfere with neuronal phenotypic expression by altering neuronal responsiveness to neurotrophic signals important for neuronal differentiation.