EFFECT OF ANTI-ESTROGEN ON STEROID INDUCED SEXUAL RECEPTIVITY IN OVARIECTOMIZED RATS

Ovariectomized female rats were injected with estradiol benzoate (EB) and 48 hr later with progesterone, in order to induce sexual receptivity as measured by the lordosis quotient (LQ) over 30 mounts. The antiestrogen CN-55, 945-27 (CN) markedly reduced the LQ when administered by gavage at the time of EB injection. There was no effect of CN when given at the time of progesterone injection, nor when given 24 hr after EB. These data demonstrate that CN counteracts the behavioral effects of EB, and suggest that exposure of the brain to EB for less than 24 hr is sufficient to trigger processes which culminate in the lordosis response of the female rat to the male. © 1968.