Effects of gonadal hormones on pacing of sexual contacts by female rats

The role of exogenous hormones in mediating pacing of reproductive encounters by ovariectomized female rats was investigated. Five estradiol benzoate (EB) treatment groups (3.3, 10, 30, 60, or 90 μg/kg) were each given five weekly tests in a two-compartment escape-reentry mating arena in the presence of three sexually vigorous males. Prior to testing, each subject received one of four dosages of progesterone (P) (1, 2, 4, or 8 mg/kg) or oil. The mean time subjects spent in the escape compartment following an intromission or ejaculation decreased for all EB treatment groups as P levels increased. The percentage of intromissions followed by retreats to the escape compartment decreased similarly for all EB treatment groups as P increased. Lordosis response increased as a function of increasing levels of EB alone or in combination with increasing levels of P.