Behavioral effects of ethanol in animals: Age differences and age changes

Ethanol-induced behavior is related to the age of the organism. This relationship has been shown for several different kinds of measures, e.g., voluntary consumption of ethanol, effects of acute and chronic administration of ethanol. The usefulness of studies concerned with voluntary ethanol consumption and aging is questioned. Usually, causal mechanisms are not determined and blood ethanol levels are not measured in these animal studies. Both acute and chronic studies have shown that old animals are more sensitive to the effects of ethanol as compared to young animals. This effect has been reported in studies employing a number of different methods of administering ethanol, e.g., injection, inhalation, liquid diet. Age-related effects in response to short-term administration of ethanol have been observed for measures such as loss of the righting reflex, general motor activity, hypothermia, and withdrawal signs. Long-term administration of ethanol has been found to affect brain chemistry, performance, and life span. Explanations for the effects of ethanol among different age groups include differences in the rate of metabolism of ethanol, the percentage of body water and lean body mass, and changes in central nervous system sensitivity. The study of the relationship between the effects of ethanol and aging is relatively new. The most obvious conclusion that can be made from a review of the literature is that much more work needs to be done. Greater attention needs to be given to the theoretical and methodological issues associated with aging research.