Selective deficits in appetitive conditioning as a consequence of ethanol withdrawal

The acquisition of a conditioned response to a cue associated with a fearful event has been shown to be impaired in animals that had been repeatedly withdrawn from ethanol, but not in animals with the same chronic ethanol treatment but only a single withdrawal episode [D. N. Stephens et al. (2001) Eur. J. Neurosci., 14, 2023-2031]. Lesion studies have shown that the amygdala plays a vital role in this type of conditioning process. Here we investigate aspects of conditioning for appetitive reinforcers in operant tasks, also shown to rely on amygdala processing, in rats following repeated withdrawal from ethanol. Rats were chronically treated with either an ethanol-containing liquid diet for 24 days continuously (single withdrawal) or interspersed with 2 x 3-day withdrawal periods (repeated withdrawal), or with a control diet (control). Two weeks after the final withdrawal, operant training began. In tasks that are impaired by lesions of the basolateral amygdala, conditioned reinforcement and reinforcer devaluation, there was no effect of chronic ethanol treatment or withdrawal on acquisition or performance. However, in a task that is dependent upon functioning of the central nucleus of the amygdala, Pavlovian-to-instrumental transfer, the single and repeated withdrawal groups were significantly impaired. Therefore, chronic ethanol treatment and withdrawal resulted in deficits in behavioural tasks that are sensitive to central but not to basolateral amygdala lesions, and may reflect different sensitivities of these areas to ethanol.