Alteration of Estrogen-Induced Lordosis through Central Administration of Corticosterone in Adrenalectomized-Ovariectomized Rats

Corticosterone was administered through various modes into several brain regions of estrogen-treated adrenalectomized-ovariectomized female rats. Daily administration of 20 micrograms corticosterone dissolved in propylene glycol through intracerebral cannulae effectively inhibited female sexual receptivity at each of four sites: third ventricle, ventro-medial hypothalamus, preoptic area, and septum. Similar administration of lesser daily doses failed to inhibit receptivity. Implantation of pure crystalline corticosterone also had no effect on receptivity at any site. Beeswax pellets chronically releasing low doses of corticosterone significantly inhibited receptivity when implanted in the medial hypothalamus and preoptic area, with similar nonsignificant trends in the lateral septum and medial forebrain bundle, but had no effect in the dorsal hippocampus or the amygdala. The effective sites are similar to those in which estrogen activity is known to induce receptivity and those in which serotonergic activity is believed to inhibit receptivity, but do not entirely correspond to sites in the brain showing the greatest uptake of corticosterone.