Increased responsiveness to ethanol with advancing age in rats.

Male CD strain rats of three different ages (young-5 months; middle-15 months; old-27 months) were tested for their responsiveness to doses of ethanol sufficient to produce hypothermia or hypnosis. Comparison dosages of ethanol across age groups were based upon the estimated equivalent dilution of the drug into the body water compartments of subjects. In the hypnosis study, there were no statistically significant differences among the groups with regard to the time elapsed until the righting reflex was lost or in total sleep time. However, old animals recovered the righting reflex in the presence of lower blood ethanol concentrations than those observed for young and middle animals, suggesting a greater sensitivity of target tissues to the hypnotic effects of ethanol in old rats. The responsiveness of old rats to the hypothermic effect of ethanol was greater than that of younger rats only when the experiment was conducted at an ambient room temperature of 10 degrees C.