, 2010). At the cellular level, distinct electrophysiological effects of glucocorticoid hormones via MRs and

GRs on hippocampal neurons have been described (Joëls and De Kloet, 1992, Pavlides et al., 1993 and Joëls et al., 2009). In this manner, the dual glucocorticoid-binding receptor system regulates the physiological (including endocrine and autonomic) responses and behavioral Compound Library concentration responses under baseline and stress conditions thereby maintaining homeostasis and facilitating long-term adaptation, together safeguarding resilience of the organism. The mechanisms underlying resilience are complex and multifaceted. Furthermore, the capacity to cope with and adapt to adverse events is influenced by life style, genetic vulnerability and early life factors. Presently, we are only beginning to understand these mechanisms. Here, we describe

several findings that portray the importance and complexity of the role of MRs and GRs in resilience. This is not a complete listing as this would go beyond the scope of this review. The described findings address the diversity and complexity of the mechanisms involved and are regarded as particularly important for future developments. The high degree of occupancy of hippocampal MRs under any physiological circumstance was a controversial finding because how would such a receptor system be able to adjust signaling to different circumstances? The answer turned out to be: by dynamically adjusting the this website concentration of receptor molecules in neurons. Serendipitously, we observed that acute stressful challenges that engage the hippocampus like forced swimming and novelty exposure resulted in a significant increase in the concentration of MRs, but not GRs, in the hippocampus of rats (Gesing et al., 2001). The

rise was transient and occurred between 8 and 24 h after the challenge. Remarkably, this effect of stress turned out to be mediated by corticotropin-releasing factor (CRF). Intracerebroventricular injection of the neuropeptide resulted in a rise in hippocampal MRs tuclazepam whereas pre-treatment with a CRF receptor antagonist blocked the effect of forced swimming on MRs. Interestingly, CRF injection was ineffective in adrenalectomized rats; concomitant MR occupancy appeared to be a necessity for CRF to produce an increase in hippocampal MR levels indicating a permissive role of the receptor in this process (Gesing et al., 2001). The observation that CRF mimicked the stress effect on MRs suggested the involvement of CRF1 receptors (Reul and Holsboer, 2002). It was indeed found that forced swimming failed to raise hippocampal MR mRNA concentrations in mice carrying a gene deletion of CRF1 receptor (Muller et al., 2003). The effect of CRF on MRs was a remarkable novel finding as we are dealing with one of the principal mediators of acute stress response in the brain, i.e. CRF, acting upon a main stress controlling instrument, i.e. MR.