A Characterization of Approach and Avoidance Learning in High-Alcohol-Drinking (HAD) and Low-Alcohol-Drinking (LAD) Rats

Abstract

This study was undertaken as one of a series of experiments designed to examine basic behavioral characteristics present in rats bred specifically for alcohol preference. The basic premise for these experiments has been the idea that alcohol-preferring and -nonpreferring rats may differ in basic activation and inhibition control mechanisms that govern behavior and that different lines of alcohol-preferring rats may demonstrate differential deficits in behavioral activation and behavioral inhibition tendencies. In the present experiment, conditioned approach and avoidance behaviors were studied in alcohol-naïve high-alcohol-drinking (HAD), low-alcohol-drinking (LAD), and N/NIH rats to evaluate behavioral activation in this line of rats. High alcohol drinking (HAD1), low alcohol drinking (LAD1), and N/Nih stock rats were trained to press a response bar during a tone signal to avoid a mild foot shock or receive a food reward. In addition, HAD2 and LAD2 rats, independently-bred replicate lines of the HAD1/LAD1 rats, were trained on the avoidance task. Although the HAD1 rats easily learned the appetitive version of the bar-pressing task, they did not learn the avoidance response. The LAD1 and N/Nih rats learned both the approach and the avoidance tasks normally. Similar to HAD1 rats, the HAD2 rats did not learn the avoidance response whereas LAD2 rats showed significant avoidance performance levels. The present data demonstrated that both HAD1 and HAD2 rats had a rather specific behavioral activation deficit: although they easily learned to press a bar to receive food reinforcement, they did not learn to press the bar to avoid a foot shock. We speculate that this failure to learn the avoidance response may be related to heightened anxiety in the HAD rats and that this excessive anxiety may lead to the development of high levels of alcohol consumption in these selectively bred rats.