Female mice lacking membrane estrogen receptor alpha display impairments in spatial memory

Abstract

Estrogens exert effects on cognition by acting on estrogen receptors (ER) including ERα. Activation of nuclear ERα results in classical genomic signaling leading to transcriptional changes that occur over hours to days. In contrast, activation of ERα localized to the membrane results in rapid signaling with effects occurring in seconds to minutes. The goal of the current study was to determine the role of membrane ERα in spatial memory. Female wildtype (WT) and transgenic mice that lack membrane ERα and express nuclear only ERα (NOER) were trained on an eight-arm radial-maze task. Following training, mice were tested on delay trials, in which delays ranging from 30 min to 5 h were inserted between the 4th and 5th arm choices. Performance was measured by number of proactive and retroactive errors. Proactive errors are short-term working memory errors defined by reentries into arms previously visited during the post-delay period or errors made during the pre-delay period. Retroactive errors are delay-dependent memory errors, defined as reentries into arms during the post-delay that were previously visited during the pre-delay. Consistent with a role for membrane ERα in rapid signaling, NOER mice made more proactive errors than WTs across all delays. NOER mice made more retroactive errors than WTs only after the 5-h delay. WT and NOER mice performed similarly on elevated plus maze and open field tests indicating no effects of membrane ERα on anxiety-related behavior or locomotor activity. Results reveal that membrane ERα plays important roles in both short-term and longer-term delay-dependent memory either directly or potentially indirectly through a role in the regulation of estradiol levels via the hypothalamic-pituitary-gonadal axis.