One of the major signal transduction systems in brain is the receptor coupled adenylated cyclase (AC) system. Work in our own laboratories, and the laboratories of others, has demonstrated that chronic ethanol ingestion reduces the ability of a number of neurotransmitters and hormones to stimulate brain adenylate cyclase activity. There is good evidence that the uncoupling of adenylate cyclase from stimulatory receptors contributes to certain aspects of alcohol tolerance and the alcohol withdrawal syndrome. Although attempts have been made using model systems of cells in culture to determine the mechanism of the ethanol-induced uncoupling of the adenylate cyclase system, the results of these studies do not seem to provide an appropriate picture of events taking place in the mammalian brain. Our studies are, therefore, focused on elucidating the mechanisms of brain-region specific changes in receptor-AC coupling after chronic ethanol administration to mice. Our mouse model system has been previously determined to reflect changes taking place in brains of human alcoholic subjects. The primary focus of our work will be on the quantitative and qualitative changes that may occur in the guanine nucleotide-binding, coupling (G) proteins, that are interposed between the receptors and the adenylate cyclase catalytic unit. We will use immunoblot (Western blot) analysis to quantitate alpha and beta subunits of Ga, Gi and Go. We will use in situ hybridization and Northern blot analysis to study the effects of ethanol on the transcripts for the various G proteins. We will also examine the functional status of G proteins from ethanol-treated and control mice be use of reconstitution assays with Gsalpha deficient cyc- cell membranes. All of these studies will be correlated in time with the development of tolerance and physical dependence on ethanol and will also be related to the obtained evidence of receptor-AC uncoupling. The studies should provide important information on how the brain adapts to the chronic presence of ethanol and how ethanol may damage brain function.