Relationship Between the Anesthetic and Gestagenic Action and Estrous Behavior-Inducing Activity of Different Progestins

Abstract

The capacities of 11 progestins to induce general anesthesia and to activate estrous behavior were studied in the ovariectomized rat. The lordosis response was used as an indicator mat the female was in heat. The different progestins were administered subcutaneously 48 hr after a standard dose of estradiol benzoate, 2.5 [mu]g/kg- The loss of the righting reflex after intravenous injection of the steroids tested was used as a criterion of anesthetic action. No correlation was obtained between the efficiency of the injected progestins to activate estrous behavior and their ability to induce general anesthesia. On the contrary, a positive correlation was revealed on comparison of the data in the estrous behavior assay and the ability to maintain pregnancy in the spayed rat. Progesterone activates estrous behavior in the estrogen-treated ovariectomized rat by a specific action on the central nervous system which is different from the general anesthetic effect.