Plasma Levels of Monoamines and Behavioral Stress: Animal Model of Depression

Background: The functions of the monoamine neurotransmitters dopamine (DA) and serotonin (5-HT) in the etiology and treatment of depressive disorders are currently an area of intense research. Much of this research has focused on a relevant animal model of depression as a means of understanding the biological mechanisms underlying human anxiety and depression. Our studies examine whether changes in plasma monoamines after single and repeated stress are associated with altered behavioral responses to inescapable shocks (IS) in a well established animal model known as learned helplessness (LH). Methods: We examined the effects of single and repeated stress on the plasma levels of cortisol, dopamine and serotonin using High Performance Liquid Chromatography with electrochemical detection (HPLC-EC). Results: We found that while levels of cortisol were increased but the levels of monoamines were significantly decreased in plasma after single and repeated stress. Conclusion: This study indicates that these two monoamine neurotransmitters systems play important roles in both the pathophysiology of depression.