RESEARCH ARTICLE Effects of omega-3 on behavioral and biochemical parameters in rats submitted to chronic mild stress Aline Haas de Mello & Aline Gassenferth & Rosiane de Bona Schraiber & Luana da Rosa Souza & Drielly Florentino & Lucinéia Gainski Danielski & Evandro da Cruz Cittadin-Soares & Jucélia Jeremias Fortunato & Fabricia Petronilho & João Quevedo & Gislaine Tezza Rezin Received: 18 February 2014 /Accepted: 13 June 2014 /Published online: 26 June 2014 # Springer Science+Business Media New York 2014 Abstract Major depression is a heterogeneous psychiatric disorder whose pathophysiology is not clearly established yet. Some studies have shown that oxidative stress and mito- chondrial dysfunction are involved in the development of major depression. Since most depressed patients do not achieve complete remission of symptoms, new therapeutic alternatives are needed and omega-3 has been highlighted in this scenario. Therefore, we have investigated the effects of omega-3 on behavioral and biochemical parameters in rats submitted to chronic mild stress (CMS). Male Wistar rats were submitted to CMS for 40 days. After the CMS period, we administered a 500 mg/kg dose of omega-3 orally, once a day, for 7 days. The animals submitted to CMS presented anhedo- nia, had no significant weight gain, presented increased levels of lipid peroxidation and protein carbonylation, and inhibition of complex I and IV activities of the mitochondrial respiratory chain. The treatment with omega-3 did not reverse anhedonia; however, it reversed weight change, increased lipid peroxida- tion and protein carbonylation levels, and partially reversed the inhibition of mitochondrial respiratory chain complexes. The findings support studies that state that major depression is associated with mitochondrial dysfunction and oxidative stress, and that omega-3 supplementation could reverse some of these changes, probably due to its antioxidant properties. Keywords Major depression . Chronic Mild stress . Omega-3 . Oxidative stress . Mitochondrial Respiratory chain Abbreviations ATP Adenosine triphosphate CMS Chronic mild stress DHA Docosahexaenoic acid EPA Eicosapentaenoic acid MDA Malondialdehyde NADH Nicotinamide adenine dinucleotide ROS Reactive oxygen species Introduction Mood disorders are among the most prevalent mental disor- ders and may result in disability, premature death and intense suffering of patients and their families (Nestler et al. 2002). Major depression affects 350 million people all over the world (World Health Organization 2012), and is characterized by single or recurrent episodes of depressed mood, loss of interest or pleasure in almost all ordinary activities, variation in appe- tite, sleep disturbance, fatigue, decreased energy, and suicide plans or attempts. In this sense, symptoms should persist for at least two consecutive weeks American Psychiatric Association APA 2000. Despite well-defined symptoms, major depression is a heterogeneous psychiatric disorder whose pathophysiology is not fully established yet (Cannon and Keller 2006). Some studies show the presence of oxidative stress and mitochon- drial dysfunction in major depression (Madrigal et al. 2001; A. H. de Mello : A. Gassenferth : R. de Bona Schraiber : L. da Rosa Souza : D. Florentino : L. G. Danielski : F. Petronilho : G. T. Rezin (*) Laboratory of Clinical and Experimental Pathophysiology, Postgraduate Program in Health Sciences, Universidade do Sul de Santa Catarina, Av. José Acácio Moreira, 787, Tubarão 88704-900, SC, Brazil e-mail: gitezza@hotmail.com E. da Cruz Cittadin-Soares : J. J. Fortunato Laboratory of Neuroscience, Postgraduate Program in Health Sciences, Universidade do Sul de Santa Catarina, Av. José Acácio Moreira, 787, Tubarão 88704-900, SC, Brazil J. Quevedo Laboratory of Neuroscience, Postgraduate Program in Health Sciences, Universidade do Extremo Sul Catarinense, Av. Universitária, 1105, Criciúma 88806-000, SC, Brazil Metab Brain Dis (2014) 29:691–699 DOI 10.1007/s11011-014-9577-5