Electron Microscopic Analysis of Hippocampal Axo-Somatic Synapses in a Chronic Stress Model for Depression

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DOI

  • David Csabai, Szentagothai Res Ctr, University of Pecs, MTA PTE, Neurobiol Stress Res Grp
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  • Laszlo Seress, Univ Pecs, University of Pecs, Sch Med, Cent Electron Microscope Lab
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  • Zsofia Varga, Szentagothai Res Ctr, University of Pecs, MTA PTE, Neurobiol Stress Res Grp
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  • Hajnalka Abraham, Univ Pecs, University of Pecs, Sch Med, Dept Mol Biol
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  • Attila Miseta, Univ Pecs, University of Pecs, Sch Med, Dept Lab Med
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  • Ove Wiborg
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  • Boldizsar Czeh, Univ Pecs, University of Pecs, Sch Med, Dept Lab Med

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 mu m 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 depressivelike 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. (C) 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.

Original languageEnglish
JournalThe Hippocampus
Volume27
Issue1
Pages (from-to)17-27
Number of pages11
ISSN1050-9631
DOIs
Publication statusPublished - Jan 2017

    Research areas

  • inhibitory synapse, hippocampus, parvalbumin, synaptic density, ultrastructure, CHRONIC MILD STRESS, PARVALBUMIN-CONTAINING INTERNEURONS, DENDRITIC SPINE DENSITY, CA3 PYRAMIDAL NEURONS, RAT HIPPOCAMPUS, ANIMAL-MODEL, EXCITATORY SYNAPSES, GAMMA OSCILLATIONS, GABAERGIC NEURONS, DENTATE GYRUS

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