HAD and LAD rats respond differently to stimulating effect but not discriminative effects of ethanol.

The drug discrimination paradigm (DD) was used to evaluate behavioral differences of rats selectively bred for differential ethanol drinking preferences. Seventh-generation high alcohol-drinking (HAD) and low alcohol-drinking (LAD) rats were trained to discriminate between ethanol (0.5 g/kg, IP) and saline vehicle, following a 2-min presession interval (PI), using an FR-10 schedule of reinforcement. The HAD line was more responsive than the LAD line to the stimulating effect of ethanol as measured by total response rates. ED50 values of 0.239 and 0.244 g/kg for the HAD and LAD lines, respectively, do not reflect any difference in the discriminative effects of ethanol. Response rates during DD indicated a dissociation of rate-increasing effects and discriminative performance following ethanol. In addition to differential drinking preference, these data suggest that selective breeding for the HAD and LAD animals also involves the stimulant action of ethanol but not on the discriminative effects.