Estrogen and progesterone dose-dependently reduce disruptive effects of restraint on lordosis behavior

Abstract

Ovariectomized rats were hormonally primed with various doses of estradiol benzoate (EB; 0.5–10 μg) in combination with various doses of progesterone (2.5–500 μg) to induce sexual receptivity. Females were then subjected to 5 min restraint and the effect on lordosis behavior was monitored for the next 30 min. Such mild stress has been previously shown to transiently reduce lordosis behavior of ovariectomized females hormonally primed only with 10 μg EB. In the current study, doses of progesterone of 25 μg or more in combination with 10 μg EB reduced the effects of restraint. Also priming doses of EB from 4.0 to 10 μg in combination with 250 μg progesterone prevented the lordosis-inhibiting effects of restraint. These findings reinforce prior observations of the dose-dependency of both estrogen and progesterone in the facilitation of lordosis behavior and introduce the female's lordosis response to mild restraint as a potentially useful index of the female's response to stress.