The Effects of Corticosteroids on Myelination of the Developing Rat Brain

Abstract

Treatment of 6-day-old Sprague-Dawley rats with a single injection of 0.8 mg of methylprednisone resulted in: (a) significant decrease in overall brain weight, which was less than the decrease in body weight; (b) decrease in frequency of myelinated fibers, which seemed to improve with age; (c) decrease in mean number of myelin lamellae, which showed only slight improvement with age, and (d) decrease in number of myelin lamellae for a given axon circumference, which did not improve with age. These alterations in myelination correlate with previous studies describing biochemical and physiologic changes in the developing brain following corticosteroid treatment and indicate that the long-term effect of neonatal corticosteroid administration warrants careful scrutiny.