17beta-Estradiol increases, aging decreases, c-Fos expression in the rat accessory olfactory bulb.

In the present paper we investigated the c-Fos immunoreactivity in the accessory olfactory bulb (AOB) of juvenile, adult and old rats of both sexes, as well as the effect of 17beta-estradiol on the expression of this immediate early gene. Basal c-Fos expression in the olfactory bulb decreased with age, and estrogen treatment caused an increase in the number of neurons expressing c-Fos in the AOB. The results indicate that both aging and estrogen have roles in the ability of neurons to co-ordinate genetic activity. Our observations may explain the decrease in age-related changes of brain plasticity, and provide data for the understanding of hormonally regulated neuronal plasticity.