animal-models-of-depression-chronic-despair-model-cdm

Animal Models of Depression - Chronic Despair Model (CDM)

Major depressive disorder is one of the most prevalent forms of mental illnesses and causes tremendous individual suffering and socioeconomic burden. ...

Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives

University of Freiburg

Conventional antidepressants have limited efficacy and many side effects, highlighting the need for fast-acting and specific medications. Induction of the synaptic protein Homer1a mediates the effects of different antidepressant treatments, including the rapid action of ketamine and sleep deprivation (SD). We show here that mimicking Homer1a upregulation via intravenous injection of cell-membrane-permeable TAT-Homer1a elicits rapid antidepressant effects in various tests. Similar to ketamine and SD, in vitro and in vivo application of TAT-Homer1a enhances mGlu5 signaling, resulting in increased mTOR pathway phosphorylation, and upregulates synaptic AMPA receptor expression and activity. The antidepressant action of SD and Homer1a induction depends on mGlu5 activation specifically in excitatory CaMK2a neurons and requires enhanced AMPA receptor activity, translation, and trafficking. Moreover, our data demonstrate a pronounced therapeutic potential of different TAT-fused peptides that directly modulate mGlu5 and AMPA receptor activity and thus might provide a novel strategy for rapid and effective antidepressant treatment.

Enhanced mGlu5 Signaling in Excitatory Neurons Promotes Rapid Antidepressant Effects via AMPA Receptor Activation.

Resilience to stress is critical for the development of depression. Enhanced adenosine A receptor (AR) signaling mediates the antidepressant effects of acute sleep deprivation (SD). However, chronic SD causes long-lasting upregulation of brain AR and increases the risk of depression. To investigate the effects of AR on mood, we utilized two transgenic mouse lines with inducible AR overexpression in forebrain neurons. These two lines have identical levels of AR increase in the cortex, but differ in the transgenic AR expression in the hippocampus. Switching on the transgene promotes robust antidepressant and anxiolytic effects in both lines. The mice of the line without transgenic AR overexpression in the hippocampus (A1Hipp-) show very strong resistance towards development of stress-induced chronic depression-like behavior. In contrast, the mice of the line in which AR upregulation extends to the hippocampus (A1Hipp+), exhibit decreased resilience to depression as compared to A1Hipp-. Similarly, automatic analysis of reward behavior of the two lines reveals that depression resistant A1Hipp-transgenic mice exhibit high sucrose preference, while mice of the vulnerable A1Hipp + line developed stress-induced anhedonic phenotype. The A1Hipp + mice have increased Homer1a expression in hippocampus, correlating with impaired long-term potentiation in the CA1 region, mimicking the stressed mice. Furthermore, virus-mediated overexpression of Homer1a in the hippocampus decreases stress resilience. Taken together our data indicate for first time that increased expression of AR and Homer1a in the hippocampus modulates the resilience to stress-induced depression and thus might potentially mediate the detrimental effects of chronic sleep restriction on mood.

Article	Year
Enhanced mGlu5 Signaling in Excitatory Neurons Promotes Rapid Antidepressant Effects via AMPA Receptor Activation. Neuron\| PubMed ID: 31420117	2019
Enhanced adenosine A receptor and Homer1a expression in hippocampus modulates the resilience to stress-induced depression-like behavior. Neuropharmacology\| PubMed ID: 31682853	2020

Tsvetan Serchov

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