Halothane-induced sleeping time in the mouse: its modification by benzodiazepines.

The conditions under which prolongation of halothane-induced sleeping time in the mouse may be used as a test for centrally acting drugs are described. The test can be recommended for its practical advantages over methods using barbiturates to induce hypnosis; due cognizance must be taken of a diurnal variation in the response of mice to halothane. To assess the usefulness of the test the effects of amphetamine, chlorpromazine, histamine, morphine, nikethamide, pentobarbitone and SKF 525A have been investigated. The interaction between 5 benzodiazepines and halothane has been studied in particular. Results from sleeping time experiments, measurements of body temperature and of brain halothane concentrations suggest that the halothane-benzodiazepine interaction is due to additive CNS depressant effects. It was found that nitrazepam and diazepam were clearly more potent than chlorodiazepoxide, medazepam and oxazepam in respect of their interactions with halothane.