Stressor-induced anhedonia in the mesocorticolimbic system

It has been suggested that uncontrollable stressors induce motivational changes in animals which are reminiscent of reward alteration in human depression. Although there is considerable support for this position, most animal models of depression do not adequately address this issue. The present review suggests that stressor-induced reductions in the rewarding value of electrical brain stimulation (ICSS) from the mesocorticolimbic system may simulate the anhedonia of human depression. The magnitude, severity and the site of these stressor-induced reward alterations within the mesocorticolimbic system vary with the strain of animal employed. The anhedonic effects of stressors are attenuated by treatments which influence mesocorticolimbic DA turnover, including systemic antidepressant and intraventricular neuropeptide administration. Although the diverse symptom profile of depression should be addressed by consideration of the constellation of behavioral disturbances induced by stressors, considerable emphasis should be devoted to an assessment of reward loss in depression. The implications of these data to the stressor depression topography and the potential role of mesocorticolimbic DA in depression and anhedonia are discussed.