Alleviation of the Negative Effects of Restraint Stress on Cognitive Learning and Retention in Rats by Estrogen and Estrogen + Progesterone

Abstract

Although the positive effects of female hormones on central nervous system function have been well documented, the actions of estrogen and progesterone on the known negative effect of stress on learning and retention have been examined in only a limited number of studies. This study used ovariectomized rats, injected with pharmacological dosages of estrogen or estrogen plus progesterone. The animals were placed in restraints to apply non-escapable stress and then were tested in a Morris water maze to evaluate cognitive learning and memory. Rats were injected, stressed and run through the maze until the maze was learned. The hypothesis was that estrogen and estrogen plus progesterone would help alleviate stress thereby increasing cognitive learning and retention. The stressed rats receiving estrogen + progesterone had a significantly increased retention compared to stressed rats. No statistically significant effects of female hormones on the alleviation of stress on learning were found.