Differential response to ethanol, pentobarbital and morphine in mice selectively bred for ethanol sensitivity

Males of two lines of mice, long sleep (LS) and short sleep (SS), that had been selectively bred for their differential sensitivity to ethanol-induced sleep, were examined for their responses to the hypothermic and analgesic effects of ethanol, pentobarbital and morphine, and to the cataleptic effect of morphine. SS mice were found to be less sensitive than the LS animals to ethanol but not pentobarbital-induced analgesia and hypothermia. The SS animals were also less sensitive to morphine-induced hypothermia, but were, by contrast, more sensitive than their LS counterparts to morphine-induced analgesia, while no line differences existed with respect to catalepsy. The rate of morphine disappearance from the blood was somewhat higher in the LS animals but this difference is probably too small to account for the observed differential responses to morphine.