ESTROGEN ENHANCES PERFORMANCE OF FEMALE RATS DURING ACQUISITION OF A RADIAL-ARM MAZE

Estrogen can influence the expression of behaviors not associated dire ctly with reproduction, including learning and memory. However, the ef fects of estrogen on learning and memory in mammals are complex, depen dent on a variety of factors. The radial arm maze is a traditional exp erimental task that takes advantage of the natural foraging strategy o f rats and provides an appropriate measure for studying the effects of estrogen on working memory in this species. In the experiments report ed here, ovariectomized rats were implanted subcutaneously with 5-mm S ilastic capsules containing 25% estradiol diluted with cholesterol. Co ntrol females received 5-mm Silastic capsules containing 100% choleste rol. Results of three separate experiments demonstrated that estradiol administered by Silastic implants for 30 days prior to eight-arm radi al maze training, during the 24 days of maze training, or both signifi cantly improved working memory performance compared to females treated with cholesterol alone, as indicated by improved arm choice accuracy over trials. The positive effect of estradiol exposure prior to traini ng suggests that estrogen may induce neuronal changes that persist bey ond the period of exposure with functional consequences for behavior, (C) 1997 Academic Press.