Double-step procedure screening for modeling reactive (exogenous) depression in rats

Depressive disorders, which show ever increasing prevalence, urgently require relevant medications. In its turn search for the antidepressant drugs requires valid animal models of depression for a drug screening. The goal of the present study was construction of affordable and simple model of reactive depression in rats, which model could be implemented in the antidepressants screening. To this end the two experimental paradigms have been modified and combined in groups of rats, which had no signs of depressive behavior. In the first experiment animals were subjected to the so-called immobilization stress. In the next step the animals, in which immobilization stress has been elicited, were introduced into the modified Forced Swim Test (FST) apparatus with an exercise wheel. Testing procedure in the FST apparatus lasted 10 min, and it was determined that 120 revs/10 min was minimal activity index for non-depressive animals, while lesser number of revolutions pointed at existence of acquired depressive status. Immobilization-induced depressive behavior was stable enough and remained two weeks following the stress. Therefore, our double-step procedure constitutes versatile, reliable, affordable, and humane screening means for modeling reactive (exogenous) depression in rats.