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Neurobiol Stress. 2019 Apr 2;10:100160. doi: 10.1016/j.ynstr.2019.100160. eCollection 2019 Feb.

Chronic mild stress induces anhedonic behavior and changes in glutamate release, BDNF trafficking and dendrite morphology only in stress vulnerable rats. The rapid restorative action of ketamine.

Author information

1
Laboratory of Neuropsychopharmacology and Functional Neurogenomics, Dipartimento di Scienze Farmacologiche e Biomolecolari and Center of Excellence for Neurodegenerative Diseases, Università degli Studi di Milano, 20133, Milan, Italy.
2
Division of Biology and Genetics, Department of Molecular and Translational Medicine, University of Brescia, 25123, Brescia, Italy.
3
Department of Pharmacy, Unit of Pharmacology and Toxicology and Center of Excellence for Biomedical Research, University of Genoa, 16148, Genova, Italy.
4
Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, 8240, Risskov, Denmark.
5
Core Centre for Molecular Morphology, Section for Stereology and Microscopy, Department of Clinical Medicine, Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University, 8000, Aarhus, Denmark.
6
Unit of Biostatistics and Biomathematics, Department of Molecular and Translational Medicine, University of Brescia, 25123, Brescia, Italy.
7
Pharmaceutical Research Centre of Excellence, School of Pharmacy, North-West University, 2520, Potchefstroom, South Africa.

Abstract

Depression is a debilitating mental disease, characterized by persistent low mood and anhedonia. Stress represents a major environmental risk factor for depression; the complex interaction of stress with genetic factors results in different individual vulnerability or resilience to the disorder. Dysfunctions of the glutamate system have a primary role in depression. Clinical neuroimaging studies have consistently reported alterations in volume and connectivity of cortico-limbic areas, where glutamate neurons and synapses predominate. This is confirmed by preclinical studies in rodents, showing that repeated stress induces morphological and functional maladaptive changes in the same brain regions altered in humans. Confirming the key role of glutamatergic transmission in depression, compelling evidence has shown that the non-competitive NMDA receptor antagonist, ketamine, induces, at sub-anesthetic dose, rapid and sustained antidepressant response in both humans and rodents. We show here that the Chronic Mild Stress model of depression induces, only in stress-vulnerable rats, depressed-like anhedonic behavior, together with impairment of glutamate/GABA presynaptic release, BDNF mRNA trafficking in dendrites and dendritic morphology in hippocampus. Moreover, we show that a single administration of ketamine restores, in 24 h, normal behavior and most of the cellular/molecular maladaptive changes in vulnerable rats. Interestingly, ketamine treatment did not restore BDNF mRNA levels reduced by chronic stress but rescued dendritic trafficking of BDNF mRNA. The present results are consistent with a mechanism of ketamine involving rapid restoration of synaptic homeostasis, through re-equilibration of glutamate/GABA release and dendritic BDNF for synaptic translation and reversal of synaptic and circuitry impairment.

KEYWORDS:

Antidepressant; BDNF; Chronic stress; Glutamate release; Ketamine; Stress vulnerability

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