Synergistic action of estradiol, progesterone and testosterone on rat proceptive behavior

The role of estradiol (E), progesterone (P) and testosterone (T) in the control of rat feminine sexual behavior (receptivity, proceptivity and sexual orientation) was analyzed. The action of estradiol benzoate (EB, 1.25 micrograms/rat x 3 days) and P (0.5 mg/rat) was compared in ovariectomized (OVX) and ovariectomized-adrenalectomized (OVX + ADX) subjects. Administration of EB alone was followed by maximum levels of lordosis behavior and a male-directed orientation in both OVX and OVX + ADX females. A reduction in the level of proceptivity was observed in EB-treated OVX + ADX animals as compared with EB-treated OVX rats. The administration of P to OVX + ADX females resulted in an increase in proceptive behavior similar to that observed in OVX EB-treated animals. A further study analyzed the effect of combined administration of EB, P and various doses of T (30, 90 and 270 micrograms/rat) in OVX + ADX rats. A synergistic action of all three hormones on proceptivity was observed. Neither a further increase in lordosis nor in male-directed orientation was observed in EB-treated females after additional treatment with P or T independently or together. Finally, we studied the effect of adrenalectomy on the spontaneous onset of estrous behavior. Adrenalectomy did not modify any aspect of normal feminine sexual behavior, suggesting that the adrenals, in the presence of the ovaries, are of no critical importance for this behavior. The possible contribution of adrenal steroids to the expression of proceptivity is discussed.