General activity from weaning to maturity in mice exposed to halothane or nitrous oxide

Mice exposed to 6 hours of 75% N2O or 0.5% halothane on the 14th day of gestation and mice exposed to 4 hours of 75% N2O or 0.5% halothane on the second day of life were tested for general activity at 3 ages. Just before weaning, all treated groups appeared hypoactive and there was a significant effect in the postnatal nitrous oxide group. Both postnatal groups had deviant distributions of scores, compared to sham-exposed controls. The main effect of treatment was greater in young adulthood, when the prenatal halothane group differed from controls. This group and the postnatal groups had excess numbers of low-scoring animals. At six months, the main effect of treatment was no longer significant, but the unusual distribution of scores was still present in the postnatal halothane group. Correlations of individual scores over the whole experiment suggested that early activity measures were significantly related to later scores. Within treatment groups, controls and postnatal nitrous oxide animals were the most consistent over time. Both agents appear to alter activity levels for periods too long to be explained by lingering presence of the drug or its metabolities.