Conditioned taste aversion induced by ethanol in alcohol-preferring rats: influence of the method of ethanol administration.

A recent study of our group has shown that ethanol evokes conditioned place preference (CPP) in Marchigian Sardinian alcohol-preferring (msP) rats following intragastric (IG) administration by means of an indwelling IG catheter, but not following administration by gavage or by intraperitoneal (IP) injection. The present study evaluated in ethanol-naive msP rats the influence of the method of administration (IG injection by indwelling catheter vs. IP injection) on ethanol-induced conditioned taste aversion (CTA). The dose of 0.35 g/kg of ethanol did not evoke aversion either by IG or by IP administration. Following IG injection, 0.7 g/kg of ethanol, the amount that msP rats voluntarily ingest in a short (2-5 min) drinking episode, did not evoke CTA, and 1.5 g/kg induced a modest CTA. On the other hand, IP injection of 0.7 g/kg of ethanol evoked CTA, and 1.5 g/kg induced a very pronounced CTA. These findings show that the aversive properties of ethanol in msP rats are influenced by the method of administration, and suggest that the IG injection by catheter may reveal more faithfully than the IP injection the motivational properties of amounts of ethanol that alcohol-preferring rats voluntarily ingest.