Place conditioning with alcohol in alcohol-preferring and -nonpreferring rats

A place-conditioning procedure was used to examine the effect of selective breeding for ethanol preference on sensitivity to the rewarding and/or aversive effects of ethanol. On 4 alternate days, groups of seven to eight alcohol-preferring (P) and alcohol-nonpreferring (NP) rats received IP injections of 0.0 (saline controls), 0.5, 1.0, or 1.5 g ethanol/kg body wt. immediately before 15-min confinement in a novel environment. On the 4 intervening days the same rats received saline injections before 15 min confinement in a different environment. On day 9, a 15-min choice test was given with no injections, in which the rats could move freely between the ethanol and the saline-paired environments. Dose-dependent avoidance of the ethanol-paired environment was observed in both lines of rats (1.0 and 1.5 g/kg), but the magnitude of the avoidance was less in the P relative to the NP rats, indicating that ethanol was less aversive for the P rats. No evidence for a place preference was observed in either line with any of the ethanol doses. An innate reduced sensitivity to the aversive effects of ethanol in rats of the P line and/or an enhanced sensitivity to the aversive effects of ethanol in rats of the NP line may contribute to the different levels of oral ethanol self-administration observed in these selectively bred rat lines.