Spatial performance and corticosteroid receptor status in the 21-day restraint stress paradigm.

Twenty-one days of restraint stress has been shown to affect hippocampal plasticity, neurogenesis, and spatial memory. Hippocampal glucocorticoid receptors (GR) and mineralocorticoid receptors (MR) are the main mediators of stress response and learning/memory processes. We studied the performance of male and female rats on a hippocampal-dependent spatial task after 21 days of restraint in relation to the stress-induced changes of GR and MR status in their hippocampi. Reduced GR immunostaining was detected in the dentate gyrus and CA1 area of stressed male rats. Stressed male rats performed worse than the male control rats on the Morris water maze. In contrast, unaltered (in the dentate gyrus) or increased (in CA1) GR immunoreactivity was seen in the hippocampus of stressed female rats. Stressed female rats had an improved memory score in the task compared with the female control rats. In addition, stressed female rats showed increased MR immunostaining in the CA3 area, which is known to be severely affected by stress. The observed sexually dimorphic effects of 21-day restraint in spatial learning and memory may be associated with the sex-dependent changes in hippocampal corticosteroid receptor status after stress.