Ethanol-produced interoceptive stimuli are time dependent in selectively bred HAS and LAS rats

Fourteenth generation high alcohol-sensitive (HAS) and low alcohol-sensitive (LAS) rats were trained to discriminate the effects of 600 mg/kg intraperitoneally administered ethanol from its vehicle at 6 and 30 min postadministration. Each of the earlier- and later-trained animals were given lower doses of ethanol and ED50 values at their trained postadministration interval were found to be nonsignificantly different. Thus, there was no difference between HAS and LAS animals as to their sensitivity to the discriminative effects of ethanol. Phase-generalization studies, where rats trained at 6 min postadministration were tested with the drug at 30 min postadministration were shown not to generalize, whereas the animals trained at 30 min postadministration and tested at 6 min postinjection were shown to readily discriminate the discriminative stimuli. This asymmetrical generalization lends evidence to the biphasic action of ethanol, and suggests that the earlier phase is quantitatively different than the latter phase. The similarity in sensitivity of the LAS and HAS animals, furthermore, suggests that the discrimination of ethanol is not based on its hypnotic effects.