Alcohol and morphine induced hypothermia in mice selected for sensitivity in ethanol.

We have used changes in body temperature as an index of responsiveness to alcohol and morphine in mice selectively bred for differential sensitivity to ethanol. In agreement with other laboratories, we found that mice which show longer duration of loss of righting reflex following hypnotic doses of ethanol (long sleep; LS) also showed greater loss in body temperature following subhypnotic doses of ethanol than did the less sensitive short sleep (SS) mice. This effect was dose dependent in both lines. In contrast, SS mice were more sensitive than LS mice to the hypothermic effects of morphine, although the difference was only evident 30 min after morphine administration. Naloxone attenuated morphine induced hypothermia in mice of both genotypes, but attenuated alcohol induced hypothermia only in SS mice. Thus, SS mice may be more sensitive to an opiate agonist and an antagonist, at least as indexed by changes in body temperature, and may prove to be a useful population for evaluating both alcohol-opiate interactions and genetic differences in opiate responsiveness.