Differences in the hypothermic response to ethanol in rats selectively bred for oral ethanol preference and nonpreference

Abstract

The duration of retention of tolerance to ethanol was tested in the alcohol-preferring (P) and alcohol-nonpreferring (NP) rats lines, using ethanol-induced hypothermia as a measure of tolerance. Rats received two injections of ethanol (3.5 g/kg) body wt, IP) and the time between the injections was 1, 2, or 3 days. When one day separated the two injections, tolerance to the hypothermic effect of a second "test" injection was found in both lines. When 2 or 3 days separated the two injections, the P line showed a loss of tolerance and the NP line showed sensitization to ethanol. Sensitization in the NP line grew stronger when the interval between injections was increased from 2 to 3 days. The duration of retention of tolerance to ethanol-induced hypothermia in the P line was shorter than has previously been reported for motor impairment in this line. It appears that the duration of tolerance retention in the P line depends on the test used to measure tolerance. Sensitization to ethanol in the NP line may be associated with low oral ethanol intake.