title: Electron Microscopic Analysis of Hippocampal Axo-Somatic Synapses in a Chronic Stress Model for Depression.
abstract: Stress can alter the number and morphology of excitatory synapses in the hippocampus, but nothing is known about the effect of stress on inhibitory synapses. Here, we used an animal model for depression, the chronic mild stress model, and quantified the number of perisomatic inhibitory neurons and their synapses. We found reduced density of parvalbumin-positive (PV+) neurons in response to stress, while the density of cholecystokinin-immunoreactive (CCK+) neurons was unaffected. We did a detailed electron microscopic analysis to quantify the frequency and morphology of perisomatic inhibitory synapses in the hippocampal CA1 area. We analyzed 1100 CA1 pyramidal neurons and 4800 perisomatic terminals in five control and four chronically stressed rats. In the control animals we observed the following parameters: Number of terminals/soma = 57; Number of terminals/100 µm cell perimeter = 10; Synapse/terminal ratio = 32%; Synapse number/100 terminal = 120; Average terminal length = 920nm. None of these parameters were affected by the stress exposure. Overall, these data indicate that despite the depressive-like behavior and the decrease in the number of perisomatic PV+ neurons in the light microscopic preparations, the number of perisomatic inhibitory synapses on CA1 pyramidal cells was not affected by stress. In the electron microscope, PV+ neurons and the axon terminals appeared to be normal and we did not find any apoptotic or necrotic cells. This data is in sharp contrast to the remarkable remodeling of the excitatory synapses on spines that has been reported in response to stress and depressive-like behavior. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.
authors: MTA - PTE, Neurobiology of Stress Research Group, Szentágothai Research Center, Pécs, 7624, Hungary.
authors: Dávid
authors: D
authors: Csabai
authors: Central Electron Microscope Laboratory, University of Pécs, Medical School, Pécs, 7624, Hungary.
authors: László
authors: L
authors: Seress
authors: MTA - PTE, Neurobiology of Stress Research Group, Szentágothai Research Center, Pécs, 7624, Hungary.
authors: Zsófia
authors: Z
authors: Varga
authors: Central Electron Microscope Laboratory, University of Pécs, Medical School, Pécs, 7624, Hungary.|Department of Medical Biology, University of Pécs, Medical School, Pécs, 7624, Hungary.
authors: Hajnalka
authors: H
authors: Ábrahám
authors: Department of Laboratory Medicine, University of Pécs, Medical School, Pécs, 7624, Hungary.
authors: Attila
authors: A
authors: Miseta
authors: Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Risskov, Denmark.
authors: Ove
authors: O
authors: Wiborg
authors: MTA - PTE, Neurobiology of Stress Research Group, Szentágothai Research Center, Pécs, 7624, Hungary.|Department of Laboratory Medicine, University of Pécs, Medical School, Pécs, 7624, Hungary.|Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Risskov, Denmark.
authors: Boldizsár
authors: 0000-0002-4926-5400
authors: B
authors: Czéh
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000378:metabolism / Q000648:ultrastructure; D002452:Cell Count; D002766:Cholecystokinin / Q000378:metabolism; D003866:Depressive Disorder / Q000378:metabolism / Q000473:pathology*; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009433:Neural Inhibition; D010320:Parvalbumins / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure*; D017966:Pyramidal Cells / Q000378:metabolism / Q000648:ultrastructure*; D017208:Rats, Wistar; D013315:Stress, Psychological / Q000378:metabolism / Q000473:pathology; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D010320:Parvalbumins; D002766:Cholecystokinin
keywords:  inhibitory synapse; hippocampus; parvalbumin; synaptic density; ultrastructure