Behavioral effects in mice exposed to nitrous oxide or halothane: prenatal vs. postnatal exposure

Mice exposed to four or six hours of nitrous oxide or halothane differed from controls on a variety of tests conducted before weaning. Whereas many agents that produce behavioral terata have very different effects at different stages of brain development, these inhalant anesthetics had similar effects, whether exposure occurred on the 14th day of gestation or two days after birth. Both treatment times and both agents were associated with delays in the appearance of developmental landmarks and delays in the appearance of righting reflexes and locomotion. The level of general activity just before weaning tended to be low in all treated groups and was significantly depressed in males exposed to N2O postnatally. The distribution of activity scores was shifted significantly in both postnatal groups compared to controls. The data are compatible with human studies suggesting that inhalants at parturition have an effect on early behavior. The persistence of effects over the first three weeks of life does not fit with the idea that the behavioral effects are mediated by continued presence of the drug. The similar effects of the two agents, which produce very different degrees of anesthesia, supports earlier studies suggesting that the teratogenicity of inhalants is independent of the level of anesthesia produced.