Operant ethanol-reinforced behavior in P, NP, HAD, and LAD rats bred for high versus low ethanol preference

These studies examined the reinforcing effects of ethanol in rats selectively bred for high versus low ethanol drinking in a two-bottle choice preference task, namely the Preferring (P), Non-Preferring (NP), High Alcohol Drinking (HAD), and Low Alcohol Drinking (LAD) rats. The results substantiate findings suggesting that genetic factors are significant in determining whether ethanol will come to serve as a reinforcer. P rats exhibited high levels of responding for ethanol compared with the water vehicle, NP and HAD rats exhibited more moderate levels of responding for ethanol, and the behavior of LAD rats suggested that ethanol served only inconsistently as a reinforcer for these rats. Overall, the results suggest the existence of distinct, biologically influenced components of ethanol drinking behavior. Preference appears to measure an inherent facilitative factor allowing animals to initiate ethanol drinking. The operant chamber paradigm appears to measure factors related to whether and to what extent ethanol will serve as a positive reinforcer following conditioned exposure to the drug. Although preferring animals generally find ethanol reinforcing there seems to be little quantitative relationship between degree of preference and whether ethanol will serve as a reinforcer. Lack of preference does not seem to be predictive of lack of reinforcement. Thus, it appears that preference for ethanol and reinforcement from ethanol are somewhat overlapping, but distinct factors that contribute to ethanol drinking. These results suggest the existence of multiple components of behavior mediated by multiple mechanisms that contribute to ethanol drinking.