Mice subjected to prolonged socioenvironmental deprivation gradually develop hyperirritability and hyperreactivity to physical stimuli. This heightened neuroexcitability may or may not debouch into aggressiveness according to strain and sex of the animals, and it is accompanied by a reduced sensitivity to CNS depressants. Socioenvironmental deprivation or isolation is shown to decrease the sensitivity either to pentobarbital or to ethanol potentiation of pentobarbital sleeping time in male mice from two different strains.