Assessment of Susceptibility of Outbred Albino Rats to the Formation of Depression-Like State of Learned Helplessness
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Susceptibility of Outbred Albino Rats to the Formation of Depression-Like State of Learned Helplessness S. O. Kotel’nikova, M. S. Sadovsky, V. A. Krayneva, E. A. Valdman, and S. B. Seredenin
Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 170, No. 8, pp. 183-187, August, 2020 Original article submitted March 17, 2020 Learned helplessness (a model of depression-like state) was developed in rats by exposure to repeated inescapable electric stimulation and evaluated by the absence of attempts to escape when it could be performed. In randomly grouped outbred white rats, 37.5% animals after the above procedure meet the criterion of learned helplessness. On experimental day 14, the latent period and the number of applied electric shocks prior to the first escape to the safe compartment in rats with learned helplessness were significantly higher than in the control, but no significant differences in these parameters were observed on day 21. The Porsolt forced swimming test performed on days 14 and 21 revealed no differences from the control group. After the rats were divided into low- and high-active subgroups according to their open field behavior, 35% rats with learned helplessness were in the low-active subgroup group and 30% rats with learned helplessness were in the high-active subgroup. On day 14, the parameters of learned helplessness significantly surpassed the control levels only in the low-active subgroup. Only in rats with learned helplessness and low activity in the open field, the immobility time in the Porsolt test was longer than in control low-active rats. These findings attest to advisability of preliminary splitting of outbred animals by their open-field behavior into low- and high-active subgroups and the use of only animals for modeling learned helplessness. Key Words: depression models; learned helplessness; Porsolt test; open-field test; rats High prevalence of depression and limited possibilities of modern pharmacotherapy of the disease explain the urgent need to search for novel and highly effective antidepressants, which logically should be based on adequate experimental models. Such models should reproduce the behavioral and neurochemical abnormalities in patients with depressive disorders. However, the diversity of etiological features, pathogenesis, and symptomatology prevents the development of consistent and comprehensive experimental translational model. At this, most researchers believe that objective description of pharmacological features and the mechanism of action of potential antidepresV. V. Zakusov Research Institute of Pharmacology, Moscow, Russia. Address for correspondence: [email protected] E. A. Valdman
sants can be achieved only by combination of various experimental models, in which learned helplessness (LH) plays an important role [9,11]. In rats, LH is formed after repeated exposure to inescapable electric shocks. This behavior is characterized by the absence of attempts to avoid or escape an aversive stimulus under conditions where it is possible to do
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