EFFECTS OF CHRONIC ETHANOL-CONSUMPTION ON G-PROTEINS IN BRAIN-AREAS ASSOCIATED WITH THE NIGROSTRIATAL AND MESOLIMBIC DOPAMINE SYSTEMS

This study examined the effects of chronic ethanol consumption on the content of G proteins in brain areas associated with the nigrostriatal and mesolimbic dopamine systems of male Fischer 344 rats, aged 3, 5, or 13 months at the time of killing. In addition, G protein mRNA was assessed in 3-month-old rats. G proteins were examined in ethanol-fed rats because a number of studies have implicated these proteins with both the acute and chronic effects of ethanol. Brain areas associated with the nigrostriatal and mesolimbic dopamine systems were examined because of the evidence that these systems are sensitive to ethanol. The brain areas examined include the substantia nigra (SN), striatum (ST), globus pallidus (GP), frontal cortex (FCX), nucleus accumbens (NA), ventral tegmental area (VTA), and ventral pallidum (VP). These experiments demonstrated that the 3 month-old rats that consumed a 6.6% (v/v) ethanol-containing liquid diet for 4 weeks had a significant (similar to 30-40%) increase in the mRNA content of G(i3 alpha) in the FCX, VTA, and VP, and a significant (similar to 20%) decrease of that for G(0 alpha) in the SN. Nonetheless, the content of the G(0 alpha) protein subunit was not altered. In addition, there were no significant differences in the content of the proteins detected by antibodies to G(s alpha), G(0 alpha), G(i1 alpha)/G(i2 alpha), and G(0 alpha)/G(i3 alpha) in the FCX, NA, and ST of similarly treated older rats (5 and 13 months). The content of mRNA for the other G proteins examined in the seven brain areas of 3-month-old rats was unaffected by chronic ethanol exposure.