HAS AND LAS RATS RESPOND DIFFERENTIALLY TO BEHAVIORAL-EFFECTS OF ETHANOL, PENTOBARBITAL, CHLORPROMAZINE AND CHLORDIAZEPOXIDE

The drug discrimination paradigm (DD) was used to evaluate differences in performance of rats selectively bred for differential sensitivity to the hypnotic effects of ethanol. Tenth generation high-alcohol sensitive (HAS) and low-alcohol sensitive (LAS) rats were trained to discriminate between ethanol (1.0 g/kg, IP) and saline vehicle on a VR-5 schedule of reinforcement. The HAS strain was more sensitive to the discriminative effects of ethanol than the LAS strain, but the magnitude of difference was much smaller than the differential sleep-time differences. The biphasic action of ethanol was differentially seen when the LAS animals exhibited increased activity during both DD and spontaneous motor activity measures and the HAS exhibited decreased activity during DD only. Pentobarbital and chlordiazepoxide but not chlorpromazine elicited the ethanol discriminative choice in both HAS and LAS strains. Response rates during DD indicated a dissociation of rate depressant effects and discriminative performance following ethanol. These findings are discussed in relationship to some current and future uses of selectively bred animal strains and DD for studying the effects of alcohol.