Simulating the anhedonia symptom of depression in animals

One of the two core symptoms of depression is anhedonia, the loss of interest or pleasure in daily activities. Stressful life events are recognized as predisposing factors in the etiology of depression. Rats subjected to a chronic, mild, unpredictable stress regimen exhibit behavioral deficits consistent with a loss of responsiveness to reward, such as decreased sucrose consumption, decreased ability to associate rewards with a distinctive environment, and decreased sensitivity to rewarding electrical brain stimulation. Normal behavior is restored by chronic treatment with antidepressants or electroshocks. Chronically stressed animals also exhibit sleep abnormalities resembling those observed in depressed patients and recognized as biological markers of depression. Thus, stress-induced anhedonia in rats represents an original animal model of some aspects of human depression offering convergent elements of biological, symptomatological, etiological, and therapeutic validity. This simulation of depression may prove useful for better understanding of the pathophysiological mechanisms involved in depressive disorders.