Forced swim and chronic variable stress reduced hippocampal cell survival in OVX female rats

Abstract

Stress and glucocorticoids induce effects on neuronal and behavioral function. These effects may depend on the study design and importantly on the nature and duration of the stressor. We have previously observed that a single exposure to the forced swim test (FST) caused long-lasting effects on the HPA axis response and hippocampal cell survival. In despite that the FST and the chronic variable stress (CVS) paradigm are not strictly comparable; the aim of this study was to compare their effects on the respective depressive-like behavior, the serum corticosterone levels and cell proliferation and survival in ovariectomized female rats. Cell proliferation was determined by Ki67-labeling, while cell survival was analyzed with BrdU, a thymidine analog. The results showed that FST increased immobility and corticosterone levels at the same time that it decreased cell survival without modifying cell proliferation. In contrast, after 5 weeks of CVS there was a sharp reduction in sucrose intake, cell proliferation and survival, but a lack of effect on corticosterone levels. The FST produced a reduction on newborn cell survival analogous to that exerted by CVS. These data suggest that the FST could be considered as an attractive model to study some kind of stress-related disorders.

Keywords: Cell proliferation; Cell survival; Chronic variable stress; Corticosterone; Forced swimming test; Ovariectomy.