Brain growth: interactions of maturation with adrenal steroids.

By performing autopsies at two different ages--when fully mature or 80 days later--it was possible to determine whether adrenalectomy-induced brain growth is enduring or transient, due to a temporary acceleration of maturation. Male rats were adrenalectomized or sham-operated at age 25 days. The effects on brain were assessed at either age 65 days or 145 days. Adrenalectomy produced the previously reported hypertrophy as reflected in hindbrain weight, forebrain weight, and linear dimensions. Most importantly, the adrenalectomy-induced brain growth not only continued across the two phases, the rate of divergence between the groups increased with age. The results clearly reject the idea that adrenalectomy merely hastens maturation of the brain. Rather, the effects of adrenalectomy are enduring, progressive, and more dramatic with age.