Mate preference and avoidance in female rats following treatment with scopolamine.

The effects of the muscarinic antagonist, scopolamine, on the behavior of female rats in a mate preference test were determined. Ovariectomized rats were primed with sufficient doses of estradiol benzoate (0.25 micrograms for 3 days) and progesterone (500 micrograms) to activate full sexual receptivity. Beginning 15 min after intraperitoneal injection of saline (0.4 ml/kg) or scopolamine hydrochloride (1 mg/kg), females were tested in an arena divided into three compartments. Females treated with scopolamine clearly avoided a compartment occupied by a gonadally intact stimulus male, instead preferring a compartment occupied by a castrated male or an empty neutral compartment. Direct contact with an intact male was a critical feature of this avoidance because females treated with scopolamine did not avoid intact males that were confined within a chamber that prevented physical contact between the male and female. Results indicate that female rats treated with scopolamine avoid direct physical contact with sexually active males, possibly due to an alteration in sexual motivation and/or the aversive nature of this interaction.