Ethanol exposure alters the phosphorylation of cyclic AMP responsive element binding protein and cyclic AMP responsive element binding activity in rat cerebellum.

The purpose of the present study was to track the acute effects of ethanol on the cerebellar adenylyl cyclase cascade from membrane to nucleus and to determine how this important signaling pathway neuroadapts during chronic ethanol exposure. An acute ethanol challenge increased cyclic AMP content and protein kinase A activity by 80% compared to control rats. In the nucleus the phosphorylated form of cAMP responsive element binding protein (CREB) increased 500%. Gel retardation assays with an oligomer encoding the rat proenkephalin cyclic AMP (CRE)1 were performed. Assays from protein derived from rats acutely exposed to ethanol identified three CRE-protein complexes also observed in assays of protein from saline-treated animals. However, after acute ethanol exposure, the intensity of the upper and middle CRE-protein complexes increased by 3-fold (280 +/- 10 vs. 70 +/- 3 arbitrary units; P < .01) compared to the sham treatment. Intensity of complex formation was still elevated 1 and 6 hr after ethanol exposure compared to sham conditions. In contrast, chronic ethanol treatment as well as pair-fed treatment did not alter the phosphorylation state of CREB or the intensity of the specific CRE-protein complexes on gel retardation assays. In summary, acute ethanol exposure resulted in the activation of the adenylyl cyclase signal transduction cascade from membrane to nucleus. In contrast, chronic ethanol exposure did not alter the phosphorylation of CREB or CRE binding activity. The behavioral significance of these events remain unclear, but may be related to the development of ethanol-induced tolerance in specific cerebellar functions.