Subchronic stress-induced depressive behavior in ovariectomized mice

Aims: Mood disorders including depression are more common in women than men, particularly in times of lower estradiol levels. in this study, we investigated the effect of estrogen on emotional behavior in mice in a stress environment. Main methods: Female mice were divided into four groups: two groups were ovariectomized (OVX) and two were sham-operated. One group each of OVX and sham mice was kept in a normal environment and the other groups were assigned to a daily stress (1 h/day) for 7 days from 5 days after operation. On the 14th day after operation, subjects were measured to assess behavioral specificity, locomotor activity, elevated plus-maze (EPM) behavior, passive avoidance (PA) behavior and forced swimming behavior. Key findings: The OVX plus stress (OVX + S) group showed a significant prolongation of immobility compared with the other groups. In all the groups there were no changes in locomotor activity, EPM behavior or PA behavior. We further examined the effect of estrogen against depressive behavior in the OVX + S group. The vehicle or 17 beta-estradiol (E2) was administered s.c. to OVX + S mice for 4 days beginning on post-operative day 11. Subchronic E2 treatment decreased the stress response and improved depressive behavior relative to the vehicle group. Significance: These data have important implications regarding the prevention of depression in postmenopausal women undergoing estrogen therapy. (C) 2009 Elsevier Inc. All rights reserved.