Abstract
Willner’s “chronic mild stress” (CMS) model is a globally recognized and most commonly used depression model. A depression model induced by ultrasonic exposure of variable frequencies has been created in our laboratory. This article compares two models of the depressive-like state according to three validity criteria. Face validity has been demonstrated in sucrose preference test, Porsolt test, social interest, open field and the Morris water maze. Rats after ultrasound impact have more pronounced anhedonia and social isolation. The construct validity has been proven due to increased levels of corticosterone, epinephrine and norepinephrine and reduced levels of dopamine and some of its metabolites in rat plasma after ultrasound exposure. Predictive validity has been described previously, where the therapeutic effects of various classes of antidepressants have been shown. Our study has demonstrated that the ultrasound-induced depression model is suitable, such as the generally accepted CMS protocol, and meets all required validity criteria. The model presented in this article might help to study pathogenetic mechanisms of depressive disorders, as well as to test promising methods of depression treatment.
Highlights
At a global level, over 4.4% of the world’s population is estimated to suffer from depression (WHO, 2017)
Rats are exposed to stressors that change unpredictably resulting in depressive-like conditions in animals (Willner et al, 1987)
Mild stress altered long term spatial memory in the same manner as ultrasound protocol. As it was emphasized by Willner, ‘‘Animal models of psychiatric states may be defined as procedures applied to laboratory animals that engender behavioral changes, which are intended to be homologous to aspects of psychiatric disorders, and can, be used as experimental tools to further the understanding of human psychopathology’’ (Willner, 2013)
Summary
Over 4.4% of the world’s population is estimated to suffer from depression (WHO, 2017). The creation of models in psychiatry has its limitations due to the exceptional specificity of the human psychology including the presence of highly differentiated structures of the neocortex that form a functional unit responsible for consciousness and thinking, as well as for speech as a second signal system (Vocate, 1987). Depressions are divided into reactive (stress-induced) and endogenous conditionally induced (Malki et al, 2014). Stress-induced models include: deprivation models, models created by pain shock, placement in extreme conditions, immobilization, forced swimming, social isolation, and mice social defeat model. Sixty-six percentage of all articles published during the year 2018 about stress-induced depression are based on Willner’s protocol. In this model, rats are exposed to stressors that change unpredictably resulting in depressive-like conditions in animals (Willner et al, 1987).
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