UNASSIGNED: Females experience @entity308 , @entity1005 ( @entity1005 ), and @entity148 at approximately twice the rate of males, but the mechanisms underlying this difference remain undefined. The effect of sex hormones on neural substrates presents a possible mechanism. We investigated the effect of ovariectomy at two ages, before puberty and in adulthood, and 17b-estradiol (E2) replacement administered chronically in drinking water on @entity148 level, fear memory formation, and extinction. Based on previous studies, we hypothesized that estradiol replacement would impair fear memory formation and enhance extinction rate. Females, age 4weeks and 10weeks, were divided randomly into 4 groups; sham surgery, OVX, OVX+low E2 (200nM), and OVX+high E2 (1000nM). Chronic treatment with high levels of E2 significantly increased @entity148 levels measured in the elevated plus maze. In both age groups, high levels of E2 significantly increased contextual fear memory but had no effect on cued fear memory. In addition, high E2 decreased the rate of extinction in both ages. Finally, @entity39325 ( @entity39325 ) is important for regulation of catecholamine levels, which play a role in fear memory formation and extinction. @entity39325 expression in the hippocampus was significantly reduced by high E2 replacement, implying increased catecholamine levels in the hippocampus of high E2 @entity19 . These results suggest that estradiol enhanced fear memory formation, and inhibited fear memory extinction, possibly stabilizing the fear memory in female @entity19 . This study has implications for a neurobiological mechanism for @entity1005 and @entity148 .

Estradiol replacement enhances fear memory formation, impairs extinction and reduces XXXX expression levels in the hippocampus of ovariectomized female @entity19 .

@entity308 :: ('MESH:D003866', 'Disease') :: ['depression'] @entity19 :: ('10090', 'Species') :: ['mice'] @entity39325 :: ('12846(Tax:10090)', 'Gene') :: ['catechol-O-methyltransferase', 'COMT'] @entity1005 :: ('MESH:D013313', 'Disease') :: ['posttraumatic stress disorder', 'PTSD'] @entity148 :: ('MESH:D001008', 'Disease') :: ['anxiety', 'anxiety disorders']
@entity39325 :: (12846(Tax:10090),Gene) :: ['COMT']
