A major challenge in ethanol research is to identify the molecular events that underlie ethanol abuse and its chronic neurologic sequelae, and to use this information to design strategies for preventing or reversing these conditions. Voltage-dependent Ca2+ channels have a fundamental role in regulating neuronal function and alterations in Ca2+ flux may be prominently involved in ethanol's effects on the nervous system. In preliminary studies, we have investigated acute and long-term modulation of Ca2+ channel function by ethanol using PC12, a clonal cell line of neural crest origin, as a model neural system. Acute exposure to ethanol inhibited K+-depolarization-evoked 45Ca2+ uptake into PC12 cells, while prolonged (2-10 days) exposure led to a reciprocal increase in 45Ca2+ uptake and in the number of Ca2+ channel binding sites labeled by the Ca2+ channel antagonist, (3H)nitrendipine. When ethanol was withdrawn from cultures, 45Ca2+ uptake returned to pre-exposure levels. These findings suggest that neuronal adaptation to ethanol may involve enhanced expression of voltage-dependent Ca2+ channels.
The specific aims of the proposed research are to investigate possible mechanisms for the acute inhibition of 45Ca2+ uptake by ethanol; examine the relationship between acute inhibition of Ca2+ flux and long-term enhancement of 45Ca2+ uptake and 3H- Ca2+ channel antagonist binding; determine whether the acute and long-term effects of ethanol are reproduced by other sedative drugs such as barbiturates and benzodiazepines; explore the possibility of modifying the long-term response to ethanol using Ca2+ channel agonist drugs; and compare the acute and long-term effects of ethanol on Ca2+ channels in undifferentiated PC12 cells, PC12 cells differentiated by treatment with nerve growth factor, and cerebral cortical neurons in primary culture. The methods to be used in these studies include PC12 cell culture, primary culture of cerebral cortical neurons, 45Ca2+ uptake assays, and 3H- Ca2+ channel antagonist binding to intact cells.
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