Restraint stress during late pregnancy in rats elicits early hypermyelination in the offspring.

Female rats were subjected to a regular, daily schedule of 2 hr of restraint stress during the final 6 days of pregnancy. During the first 2 postnatal weeks, adrenal weights were greater than normal in the offspring of the stressed dams. The concentration of brain myelin was higher than control at 14 and 21 days of age but similar to normal by day 40. Early hypermyelination may be partly responsible for early motor development, as previously observed in prenatally stressed rats.