A halothane-related effect on rat brain myelination: a comparison of chronic prenatal or postnatal exposure.

Rats were exposed to 0.5% halothane in air for 8 h per day during the intervals (1) 5 days postconception to birth, (2) birth to 5 days postnatal age, or (3) birth to 10 days postnatal age. Controls were exposed to an equivalent flow of air. Prenatal exposure had no significant effect on body or brain weight and no subsequent effect on the relative synthesis of brain subcellular membranes. Five days of postnatal exposure caused a 10% reduction in body and brain weight and a 10% relative reduction in the synthesis of brain myelin. The effect persisted throughout the period rapid postnatal brain myelination. Ten days of postnatal exposure produced equivalent, more severe effects on body and brain weights and a more severe effect on myelin synthesis. Postnatal exposure had no apparent effect on the relative synthesis of non-myelin particulate proteins.