Ethanol enhancement of Pavlovian conditioning: comparison with instrumental conditioning.

Yoked pairs of rabbits received conditioning and extinction of eyeblink and heart rate responses using aversive Pavlovian versus instrumental avoidance contingencies. A low dose of ethanol (375 mg/kg) increased the amplitude of conditioned eyeblink responses during training and during subsequent extinction following either ethanol or water; this effect was more pronounced in the Pavlovian than the instrumental contingency groups. Ethanol treatment did not affect the cardiac component of the Orienting Reflex to novel tones or heart rate conditioned responses to tone signals, but did bias heart rate responses to tone-shock stimulus pairs in a parasympathetic direction; this effect occurred in both contingency groups but appeared to involve associative factors. These results support the conclusion that mild ethanol intoxication enhances the acquisition of Pavlovian conditioned reflexes, and impairs the ability to modify these responses when stimulus contingencies later change.