Brain region specificity in estradiol effects on neuronal ultrastructure in rats.

The effects of long-term (15 days) and short-term (3 days) treatment with estradiol benzoate (EB) on stacking of rough endoplasmic reticulum in neurons of four brain regions (medial preoptic nucleus, ventromedial hypothalamus, arcuate nucleus and midbrain central gray) were investigated. These regions were chosen for their role in reproduction in female rats and/or the presence of estradiol-concentrating cells. Long-term EB treatment increased the proportion of neurons in the ventromedial hypothalamus (by 30%) and medial preoptic nucleus (by 17%) that contained stacks of rough endoplasmic reticulum. Short-term EB affected stacking only in ventromedial hypothalamic neurons. EB was without effect on neurons of the arcuate nucleus of the hypothalamus or midbrain central gray. The degree of stacking of rough endoplasmic reticulum in neurons of the ventromedial hypothalamus was positively related to the level of sexual behavior (lordosis) activated by these hormone treatments.