A Methodological Review of Development and Assessment of Behavioral Models of Depression in Rats

Depression is a chronic, multifactorial, and potentially life-threatening mental disorder that affects up to 20% of the worldwide population. Over several decades, numerous animal models have been established to study the underlying pathophysiology of depression and to test novel antidepressant treatment strategies. The criteria for identifying animal models of depression based on two principles: the side effects of antidepressants and responses to stress. Here, we summarized depression animal models, including learned helplessness, chronic mild stress, social defeat paradigms, and early life stress. Also, we reviewed the behavioral tests for screening antidepressants, such as forced swimming test, tail suspension test, sucrose preference test, open field test, elevated plus maze test, novelty-induced hypophagia, intracranial self-stimulation, and dark/light box test.
The complexity of the depression and its etiologic as well as pathophysiological similarities with anxiety disorders challenge the developing of a comprehensive animal model that accurately reflect different aspects of depression. However, these animal models could so far help in a better understanding of the pathophysiology of depression.