it is clear that factors other than basal DA levels are involved. For example, alcohol-preferring AA rats showed higher levels of mu-opioid binding in PFC under drug-naive conditions than did alcohol-avoiding ANA rats, as well as higher levels of proenkephalin mRNA (Marinelli et al., 2000). Differences have also been observed in PFC 5-HT receptor levels in PFC between strains and sP rats demonstrated lower levels of basal 5-HT2A-binding sites than sNP animals (Ciccocioppo et al., 1997). Given the powerful effects of these neurotransmitters on PFC function, it is likely that differences in expression or functional activity of these neuromodulators is important in shaping the PFC’s response to ethanol.
