Effects of individual stressors used in a battery of “chronic unpredictable stress” on long-term plasticity in the hippocampus of juvenile rats

Alexandra A Gorbunova,Margarita R Novikova,Anna O Manolova,Mikhail Yu Stepanichev,Natalia V Gulyaeva,Irina V Kudryashova

doi:10.21307/ane-2017-058

Abstract

We have studied alterations in the properties of long-term potentiation (LTP) in hippocampal slices of juvenile rats induced by the exposure of animals to different individual stressors usually used in batteries of chronic unpredictable stress (CUS), a widely used model of depression. Social isolation for 16 h did substantially affect neither the magnitude and nor the development of LTP. The effects of stroboscopic illumination and water deprivation appeared most severe, though opposite: the first stressor had activating effect, whereas the second one inhibited the development of LTP. In addition to the effects of these factors on the LTP magnitude, they also affected the patterns of LTP development. In this study weak tetanization with different probability of maintenance was used, and most of stressors, in spite of the similar LTP magnitude, influenced significantly on the process of consolidation. In hippocampal slices from rats maintained on wet bedding for 16 h, the time course but not magnitude of LTP significantly differed from that observed in the control or socially isolated rats. The weakest effect on LTP was observed in hippocampal slices of the rats exposed to food deprivation. In these animals, only some differences were observed in the development of LTP as compared to socially isolated rats. These data allow ranging stressors used in CUS paradigms according to the severity of their potential effects on neuronal function and animal behavior.

Highlights

Depression is a common mental disorder, characterized by sadness, loss of interest or pleasure, feelings of guilt or low self‐worth, disturbed sleep or appetite, feelings of tiredness, and poor concentration (WHO Depression, 2016)
In order to evaluate the effect of short‐term social isolation, the long‐term potentiation (LTP) properties were studied in the control rats and rats isolated for 16 h
The magnitude increased by 113–208% of the base‐ line observed prior to tetanization, while in the isolated group, the LTP magnitudes varied within 136–296% of the baseline level

Summary

Introduction

Depression is a common mental disorder, characterized by sadness, loss of interest or pleasure, feelings of guilt or low self‐worth, disturbed sleep or appetite, feelings of tiredness, and poor concentration (WHO Depression, 2016). The rats exposed to this protocol exhibited anhedo‐ nia, an important symptom of depressive disorders Later on, this protocol was modified by Willner et al (1987) who exposed animals to a battery of stressful factors, specifical‐ ly food and water deprivation, stroboscopic illumination, inclined cage, wet bedding, and some other so called mild stressors in order to induce anhedonia‐like behavior. This protocol was modified by Willner et al (1987) who exposed animals to a battery of stressful factors, specifical‐ ly food and water deprivation, stroboscopic illumination, inclined cage, wet bedding, and some other so called mild stressors in order to induce anhedonia‐like behavior This model was successfully adopted in several laboratories (Holderbach et al 2007, Luo et al 2008, Wang et al 2008), including our lab (Stepanichev et al, 2016).

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Conclusion