A single administration of ethanol simultaneously increases c-fos mRNA and reduces c-jun mRNA in the hypothalamus and hippocampus.

We have previously demonstrated that a single administration of ethanol induces the expression of c-fos mRNA in the hypothalamic paraventricular nucleus (PVN). However, Fos protein must interact with a member of the Jun family to form functional heterodimers. To determine whether ethanol may have differential effects on c-fos and c-jun expression, we injected male rats acclimated to a 25 degrees C environment with ethanol (3 g/kg b.wt.) or saline. Using in situ hybridization histochemistry with oligonucleotide probes, we found that ethanol increased c-fos mRNA in the PVN, but decreased c-jun mRNA both in the PVN and in hippocampus. Considering that ethanol produces hypothermia and that the PVN contains neurons activated during hypothermia, we evaluated the effect of cold on c-fos and c-jun mRNA. Both cold and ethanol increased c-fos mRNA, and the effects were additive. However, c-jun mRNA levels in both PVN and hippocampus were unaffected by temperature. Finally, c-jun mRNA levels in the hippocampus were significantly reduced by chronic ethanol exposure, and this trend was also observed in the PVN. These findings demonstrate that a single injection of ethanol has opposite effects on the expression of nuclear transcription factors which interact to regulate gene expression in the nervous system.