Ethanol modulates GABAB receptor expression in cortex and hippocampus of the adult rat brain

Using in situ hybridization, RNase protection assay and Western blot, we studied the effects of ethanol on the expression levels of GABAB receptor mRNA and protein in the cortex and hippocampus from adult rat brain. The results showed that ethanol significantly increased GABAB1 and GABAB2 receptor protein expression in the cortex, whereas only GABAB2 was increased in the hippocampus. GABAB receptor agonist baclofen could partially reverse the effect of ethanol. Further studies of the mRNA levels defined that GABAB1 mRNA levels were significantly increased in the hippocampus, with no significant changes of GABAB2 mRNA levels. Moreover, GABAB1 and GABAB2 receptor mRNA levels were increased on 3-week ethanol treatment. Finally, GABAB agonist baclofen and antagonist phaclofen showed significant decreasing effects on GABAB1 receptor mRNA levels in the cortex, but not in the hippocampus. These results were further confirmed by in situ hybridization. Thus, the present results showed the effects of ethanol on GABAB receptors in the cortex and hippocampus, implying the possible role of GABAB receptor in ethanol effects. The effects of GABAB receptor agonist and antagonist suggested that the possible mechanisms underlying that GABAB receptor modulated the behavioral effect induced by ethanol.