The role of drug-paired stimuli in extinction and reinstatement of ethanol-seeking behaviour in the rat

Male Wistar rats were trained to respond for ethanol (30 min/day) in an ora l self-administration procedure. A single lever press resulted in presentat ion of 0.1 ml of 8% ethanol from a liquid dipper. When responding for ethan ol stabilised, reinstatement sessions started. In the 30-min reinstatement session, lever pressing was first extinguished for 20 min by switching the dipper off. Then. different kinds of stimuli were non-contingently delivere d and reinstatement of lever pressing was assessed. Fifteen random (random time = 15 s) presentations of the dipper containing 8% ethanol potently rei nstated ethanol-seeking. The reinstatement of lever pressing was immediate and most responses were emitted during the time needed for the first five p resentations to occur. Presentations of the empty dipper or delivery of a n on-specific stimulus (high-amplitude tone) did not produce any reinstatemen t. These results indicate that non-contingent presentations of the ethanol- associated stimulus complex may reinstate operant behaviour previously rein forced with ethanol. (C) 1999 Elsevier Science B.V. All rights reserved.