EFFECTS OF LONG-TERM ESTRADIOL EXPOSURE ON THE HYPOTHALAMIC NEURON NUMBER

Neuron density, volume of the area and total neuron number were measur ed in the medial preoptic area, anterior hypothalamic area and arcuate nucleus of the hypothalamus of young (6-month-old), middle age (14-mo nth-old) and old (22-month-old) male and female rats. Intact male rats did not show neuron loss even in old age, while intact female rats ma nifested neuron loss in the medial preoptic area, anterior hypothalami c area and arcuate nucleus in old age. Long-term administration of est radiol benzoate to castrated male rats induced neuron loss in the ante rior hypothalamic area and arcuate nucleus of the middle age group and in all three areas of the old age group. However, long-term ovariecto my could not prevent neuron loss in these hypothalamic areas in old ag e. The results suggested that estradiol can have a cumulative impact o n the degree of neuron damage and simulate female-type age-related neu ron loss in male rats and that there may be the possibility of an intr insic aging process inducing neuron loss in female rats.