Temporal and spatial dynamics of corticosteroid receptor down-regulation in rat brain following social defeat.

The experiments explored the nature and time course of changes in glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) binding in homogenates of various brain regions and pituitary of male Wistar rats following social defeat stress. One week after defeat, the binding capacity of GRs was decreased in the hippocampus and the hypothalamus while no changes were observed in the parietal cortex and the pituitary. The number of MRs remained at the same level as in undefeated rats. Three weeks postdefeat, the initially down-regulated GR returned to baseline level in the hippocampus and the hypothalamus. However, GR binding was now decreased in the parietal cortex. Severe down-regulation of MRs was detected in the hippocampal and septal tissue. The results show that brief but intense stress like social defeat induces a long-lasting down-regulation of corticosteroid receptors and that the temporal dynamics of these changes are not only differential for GRs and MRs but also for brain sites.