Abstract
17beta-Estradiol (E(2)) may influence cognitive and/or affective behavior in part via the beta isoform of the estrogen receptor (ERbeta). Endocrine status and behavior in cognitive (object recognition, T-maze), anxiety (open field, elevated plus maze, mirror maze, emergence), and motor/coordination (rotarod, activity chamber) tasks of proestrous and diestrous wildtype (WT) and ERbeta knockout (betaERKO) mice was examined. Proestrous (WT or betaERKO), versus diestrous, mice had higher E(2) and progestin levels in plasma, hippocampus, and cortex. The only effect of genotype on hormone levels was for corticosterone, such that betaERKO mice had higher concentrations of corticosterone than did WT mice. Proestrous WT, but not betaERKO, mice had improved performance in the object recognition (greater percentage of time with novel object) and T-maze tasks (greater percentage of spontaneous alternations) and less anxiety-like behavior in the plus maze (increased duration on open arms) and mirror chamber task (increased duration in mirror) than did diestrous mice. This pattern was not seen in the rotarod, open field, or activity monitor, suggesting effects may be specific to affective and cognitive behavior, rather than motor behavior/coordination. Thus, enhanced performance in cognitive tasks and anti-anxiety-like behavior of proestrous mice may require actions of ERbeta in the hippocampus and/or cortex.