Effect of isolation on barbiturate anaesthesia in the rat.

The duration of barbiturate-induced sleeping in rats was found to be reduced by isolation housing. It was also lower in males than females, and lower in the dark phase of the diurnal cycle. These variables were shown to be additive in their effects. Sex differences in barbiturate action were found to be reduced by gonadectomy in males; and the effects of isolation were found to depend upon housing conditions at the time of testing rather than upon early rearing environment. The implication for theories of arousal is discussed.