Influence of age on the development of rapid tolerance to ethanol

Fischer-344 rats of three different ages (4, 13, and 25 months) were tested to determine the extent and duration of rapid tolerance to ethanol-induced hypothermia and hypnosis. There were no significant differences among groups with regard to maximal ethanol hypothermia (3.0-3.5 g/kg ethanol), nor did any of the groups display a significant change (rapid tolerance) in the maximal hypothermic response when tested with a second identical challenge 48 h later. Rapid tolerance to ethanol hypnosis was observed across groups at 48 h, utilizing two different dosing schemes. No tolerance was observed if 14 days were allowed to elapse between the initial and the test challenge. Young rats were observed to develop a greater degree of rapid tolerance than did middle-aged or old rats, using hypnosis as a measure.