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 glucocort icoid receptor (GR) and mineralocorticoid receptor (MR) binding in homogena tes of various brain regions and pituitary of male Wistar rats following so cial defeat stress. One week after defeat, the binding capacity of GRs was decreased in the hippocampus and the hypothalamus while no changes were obs erved in the parietal cortex and the pituitary. The number of MRs remained at the same level as in undefeated rats. Three weeks postdefeat, the initia lly 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 t issue. The results show that brief but intense stress like social defeat in duces a long-lasting down-regulation of corticosteroid receptors and that t he temporal dynamics of these changes are not only differential for GRs and MRs but also for brain sites. (C) 2001 Elsevier Science Inc. All rights re served.