Effect of chronic ethanol treatment of Ca2+-inhibited adenylyl cyclase in mouse striatum

In the present study, to investigate the possibility that chronic ethanol treatment might alter Ca2+-inhibited type 5 adenylyl cyclase (AC) activity, we examined the effect of chronic ethanol treatment on striatal dopaminergic signal transduction, especially the AC system, in mice. We fed male C57BL/6 mice for 7 days with a 5% ethanol-containing or control liquid diet. Basal and forskolin-stimulated AC activities were reduced in striatal membranes of ethanol-treated mice. 5'-guanylylimidodiphosphate-stimulated AC activity was also decreased in ethanol-treated mice. But no significant differences were observed in the levels of the guanine nucleotide binding protein subunits Gs alpha and Gi1alpha&2alpha, determined by immunoblotting, between ethanol-treated and control mice. These results indicated that the function of the catalytic subunit of AC was decreased in the straitum of chronically ethanol-treated mice. We further examined the inhibitory regulation of AC activity in the context of a change of type 5 AC. Inhibition of forskolin-stimulated AC activity by 10 microM free Ca2+ was smaller in ethanol-treated mice than in control mice. However, the protein level of type 5 AC in the striatum, determined by immunoblotting, was not significantly different between ethanol-treated and control mice. These findings suggest that Ca2+-inhibited, presumably type 5, AC activity is reduced in mouse striatum by chronic ethanol treatment, and that this reduction is not due to a decrease in type 5 AC expression.