Ethanol enhancement of Pavlovian conditioning.

Rabbits were tested for Pavlovian conditioning and extinction of eye blink and heart rate responses, following water or various doses of ethanol (375-1,500 mg/kg, po). The highest dose suppressed both eye blink and heart rate conditioning during training, whereas the lowest dose enhanced heart rate responses during training and increased eye blink responses during later extinction in a symmetrically state-dependent manner. An intermediate dose (750 mg/kg) administered during training enhanced heart rate responses and suppressed eye blink responses but increased eye blink responses during later extinction following either ethanol or water. Ethanol treatments also suppressed unconditioned responses to shock and increased locomotor activity in rabbits; however, these effects differed qualitatively from those that occurred during Pavlovian training and extinction. These results suggest that very low doses of ethanol can enhance the ability of stimuli to elicit Pavlovian conditioned reflexes and impair the ability to adaptively modify these reflexes when stimulus contingencies later change.