Endocrinology, Vol 116, 2393-2399, Copyright © 1985 by Endocrine Society

ARTICLES

Diencephalic sites of progesterone action for inhibiting aggression and facilitating sexual receptivity in estrogen-primed golden hamsters

LK Takahashi and RD Lisk

Diencephalic sites of action of progesterone (P) responsible for inhibiting aggression and facilitating sexual receptivity were examined in ovariectomized golden hamsters primed with Silastic capsules of estradiol. P was applied centrally by inserting a hormone-filled, 27- gauge cannula into a 22-gauge guide cannula that was implanted unilaterally in the medial preoptic area (MPO), the anterior hypothalamus (AH), or the ventromedial hypothalamus (VMH). Control implants consisted of cholesterol-filled cannulae placed within the same regions of the brain. Tests for sexual and aggressive behavior occurred 1, 2, 4, and 6 h after hormone implantation by introducing a sexually experienced male into the home cage of the female. Nine of 20 females with P in the VMH exhibited lordosis in comparison to 1 of 12 females in the MPO group and 5 of 16 animals in the AH group. The induction of sexual responsiveness after P implantation in the VMH was further demonstrated in 6 of 11 ovariectomized-adrenalectomized females, indicating that the observed receptivity was not contingent upon activation of the hypothalamic-pituitary-adrenal axis. In addition to the receptive promoting action of P in the VMH, P implantation in the MPO and VMH but not in AH regions was highly effective in inhibiting female biting attacks upon males. In summary, these findings indicate that P can both facilitate sexual receptivity and inhibit aggressive behavior and that P induces these changes in behavior at different locations in the diencephalon.