Potential role of the gene transcription factor cyclic AMP-responsive element binding protein in ethanol...

This investigation examined the effects of acute and chronic ethanol exposure and its withdrawal on the cAMP-responsive element binding protein (CREB) and the activator protein-1 (AP-1) gene transcription factors in the rat brain. The anxiogenic effects of ethanol withdrawal after acute or protracted ethanol treatment of rats were measured by the elevated plus-maze (EPM) test. It was observed that ethanol withdrawal after acute ethanol treatment has no effect on open-arm activity (percent of open-arm entries and the mean percent of time spent on the open arms) of rats on the EPM test. On the other hand, the time course studies of the development of anxiety during ethanol withdrawal (0, 12, 24, and 72 h) after 15 days of ethanol treatment indicate that peak anxiety (significant decrease in open-arm activity) occurred at 24 h of ethanol withdrawal in rats. It was observed that acute ethanol treatment and its withdrawal (24 h) had no effect on CRE- or AP-1 DNA-binding activities in the rat cortex as determined by the electrophoretic gel-mobility shift assay. It was also found that chronic ethanol treatment and its withdrawal (24 h) had no effect on AP-1 DNA-binding activity in the rat cortex. Investigation of the time course studies of changes in CRE-DNA-binding activity during ethanol withdrawal (0, 12, 24, and 72 h) after 15 days of ethanol treatment indicated that the peak reduction of CRE-DNA-binding activity occurred at 24 h of ethanol withdrawal. The changes in the immunolabeling of the CREB-related target, that is, brain-derived neurotrophic factor (BDNF), in the rat cortex during chronic ethanol treatment and its withdrawal (24 h) were examined using western blotting. It was found that 24 h but not 0 h of ethanol withdrawal after 15 days of ethanol treatment caused a significant decrease in the immunolabeling of BDNF in the rat cortex. Fluoxetine (alone) treatment of rats for 1 or 15 days had no effect on open-arm activity and cortical CRE-DNA-binding activity. However, when fluoxetine was administered concurrently with ethanol treatment for 15 days, it caused a reversal of the anxiogenic effects of ethanol withdrawal and antagonized the down-regulation of CRE-DNA-binding activity and of the decrease in immunolabeling of BDNF in the cortices of ethanol-withdrawn rats. On the other hand, acute fluoxetine treatment produced normalization of the reduction of cortical CRE-DNA binding in ethanol-withdrawn rats (24 h) but did not reach the level of significance compared with normal control rats. Acute fluoxetine treatment had no effect on anxiety in ethanol-withdrawn rats. Taken together, these results suggest the possibility that decreased CRE-DNA-binding activity in the rat cortex may be associated with the molecular mechanisms of ethanol dependence (i.e., ethanol withdrawal-related anxiety).