Glucocorticoid hormones have important effects on brain function in the context of acute and chronic stress. Many of these are mediated by the glucocorticoid receptor (GR). GR has transcriptional... Show moreGlucocorticoid hormones have important effects on brain function in the context of acute and chronic stress. Many of these are mediated by the glucocorticoid receptor (GR). GR has transcriptional activity which is highly context-specific and differs between tissues and even between cell types. The outcome of GR-mediated transcription depends on the interactome of associated coregulators. Selective GR modulators (SGRMs) are a class of GR ligands that can be used to activate only a subset of GR-coregulator interactions, thereby giving the possibility to induce a unique combination of agonistic and antagonistic GR properties. We describe SGRM action in animal models of brain function and pathology, and argue for their utility as molecular filters, to characterize context-specific GR interactome and transcriptional activity that are responsible for particular glucocorticoid-driven effects in cognitive processes such as memory consolidation. The ultimate objective of this approach is to identify molecular processes that are responsible for adaptive and maladaptive effects of glucocorticoids in the brain. Show less
The results in this thesis showed for the first time doublecortin-like (DCL)-specific expression in the adult mouse brain. Besides the expected regions with the capacity to generate new neurons ... Show moreThe results in this thesis showed for the first time doublecortin-like (DCL)-specific expression in the adult mouse brain. Besides the expected regions with the capacity to generate new neurons (hippocampus and olfactory forebrain), DCL expression was found in three novel brain areas namely hypothalamic tanycytes, suprachiasmatic nucleus and Islands of Calleja. A state of the art conditional shRNA expressing mouse model was used to target DCL mRNA. The analysis of these DCL knockdown animals using qPCR and Western blot revealed strong reduction of DCL protein expression. Subsequent stereological analysis using BrdU and several stem cell and neuronal markers revealed increased progenitor proliferation, but impaired neurogenesis in the hippocampus. This impaired neurogenesis was associated, however, with an apparent normal spatial and contextual fear memory formation in circular hole board and in a contextual fear conditioning paradigm. Therefore, DCL-regulated adult neurogenesis seems not crucial for hippocampus-dependent learning. However, more subtle functions like pattern separation and context distinction might be regulated by DCL. DCL knockdown also increased D2 activity within the hypothalamus. Altogether, the DCL-KD mouse seems a good working model to study adult neurogenesis and the role of DCL in this process. Show less
Chronic stress is considered a vulnerability factor for depression. A key symptom is anhedonia; a reduced response to positive stimuli. Drugs are effective for only 20-40% of the patients and new... Show moreChronic stress is considered a vulnerability factor for depression. A key symptom is anhedonia; a reduced response to positive stimuli. Drugs are effective for only 20-40% of the patients and new drugs are urgently needed. The objective of the research was to develop a mouse model of depression that would express anhedonia, induced by chronic stress. Mice were repeatedly exposed to the non-physical presence of a rat. Alterations in stress system activity were measured. Anhedonia was assessed by studying the behavioral response to positive stimuli. As a potential therapeutical approach we assessed reward expectation, and studied the effect of repeated administration of mifepristone (glucocorticoid receptor antagonist), directly targeting stress system regulation. Our model induced changes in the sensitivity of the reward system that contributed to cognitive impairments underlying anhedonia. The effects could partially be restored by additional reward. Mifepristone in na_ve mice suppressed stress system activity, which could indicate a similar direction of effects in stressed mice if provided. Concluding, our chronic stress mouse model induces anhedonia. The new methodology to reduce stress by either providing additional positive stimuli or mifepristone, increases the well being of the mice and may prove a new drug target to treat depression in humans. Show less
