Alpha-methyltyptamine blocks facilitation of lordosis by progesterone in spayed, extrogen-primed rats

Alpha-methyltryptamine, a drug which stimulates serotonergic receptors in the central nervous system, inhibited the induction of sexual receptivity in spayed female rats by estradiol benzoate and progesterone. The drug had no effect on the sexual receptivity induced by estradiol benzoate alone. These data are consistent with the hypothesis that progesterone facilitates lordosis in estrogen-primed rats by inhibiting a serotonergic system in the brain. The data also suggest that estradiol and progesterone act on separate neurochemical systems to induce estrous behavior in rats.