The oligomeric GABA/A receptor-ionophore complex belongs to ligand-gated ion-channel gene family, and it is a site of action for a variety of centrally acting drugs including ethanol. Recent molecular biological studies have demonstrated heterogeneity of GABA/A receptors, especially in terms of the distribution of alpha subunits in the CNS. The proposal is an extension of ongoing studies aimed at understanding and defining the involvement of GABA receptor system in the actions of ethanol. This will be achieved by using radioligand binding studies, ion flux studies, photoaffinity labeling, and measuring mRNA levels by Northern blot analysis. These studies will be conducted in parallel in well characterized mammalian cultured spinal cord neurons (alpha3, alpha2 and/or alpha 4 abundant) and cortical neurons (alpha1 abundant). We will determine if ethanol modulates GABA/A ergic transmission in a similar or different ways in these two varied forms of GABA/A receptors. Studies are also proposed to determine if chronic ethanol induced upregulation of inverse agonist benzodiazepine binding sites can be correlated with changes in mRNA levels of different subunits (alpha, beta, gamma2) of GABA/A receptors in spinal cord and cortical neurons. Similar chronic ethanol studies will be conducted in rat brain regions. Additionally, we will determine if GABA/B receptors are involved in ethanol modulation of GABA/A ergic transmission or in the actions of ethanol. This will be investigated by determining: a) if GABA/3B receptor agonists or antagonists modulate ethanol interactions with GABA-induced Cl-influx; b) if GABA/B receptor coupled G-proteins are involved in ethanol's effect on GABA/A mediated responses; and c) if ethanol has any facilitatory effect on GABA/B receptor mediated presynaptic or postsynaptic effects, using new 86Rb-flux assays, developed in our laboratory. The proposed studies are aimed at increasing our understanding of the involvement of two varied forms of GABA/A receptor system and GABA/B receptors in the actions of ethanol.
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