Motivational properties of ethanol in naive rats as studied by place conditioning

The reinforcing properties of ethanol were examined in naive adult male rats by means of a place conditioning paradigm that has previously demonstrated the positive reinforcing properties of food, water and some drugs, and the aversive properties of punishers such as electric shock and lithium chloride. Only doses of 0.8-1.0 g/kg and higher produced clear place conditioning, and this was only conditioned place aversion; rats spent significantly more time on the side of the place conditioning box in which they received the vehicle than on the side in which they received ethanol. Doses between 0.1 g/kg and 0.8 g/kg produced increases in general activity, but did not produce any place conditioning. Control experiments indicated that the pattern of effects was not specific to the route of ethanol administration (intravenous or intragastric), rate of infusion, concentration, or vehicle. It was concluded that ethanol, in the doses used here, has only punishing or neutral motivational effects in naive rats and does not serve as a primary positive reinforcer in this model. The conclusions are discussed in relation to the relative difficulty encountered in attempts to produce ethanol self-administration, and the findings are viewed as consistent with a proposal that prolonged training and experience with ethanol are important for ethanol self-administration by the rat.