Behavioral despair associated with a mouse model of Crohn's disease: Role of nitric oxide pathway Pouria Heydarpour a,b,1 , Reza Rahimian a,c,1 , Gohar Fakhfouri c,d , Shayan Khoshkish a,b , Nahid Fakhraei b , Mohammad Salehi-Sadaghiani a,b , Hongxing Wang e , Ata Abbasi f , Ahmad Reza Dehpour a,g , Jean-Eric Ghia e,h, ⁎ a Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, P.O. Box 13145-784, Tehran, Iran b Brain and Spinal Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran c Department of Psychiatry and Neuroscience, Faculty of Medicine, Laval University, 1050, avenue de la Médecine, Québec City, Québec, Canada d Institut universitaire en santé mentale de Québec, 2601, Chemin de la Canardière, Québec City, Québec, Canada e Department of Immunology, University of Manitoba, Winnipeg, Manitoba, Canada f Department of Pathology, Urmia University of Medical Science, Urmia, Iran g Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran h Department of Internal Medicine section of Gastroenterology, and Inflammatory Bowel Disease Clinical & Research Center, University of Manitoba, Winnipeg, Manitoba, Canada abstract article info Article history: Received 3 June 2015 Received in revised form 24 July 2015 Accepted 7 August 2015 Available online 9 August 2015 Keywords: Behavioral despair Inflammatory bowel disease Nitric oxide TNF-α Crohn's disease (CD) is associated with increased psychiatric co-morbidities. Nitric oxide (NO) is implicated in inflammation and tissue injury in CD, and it may also play a central role in pathogenesis of the accompanying be- havioral despair. This study investigated the role of the NO pathway in behavioral despair associated with a mouse model of CD. Colitis was induced by intrarectal (i.r.) injection of 2,4,6-trinitrobenzenesulfonic acid (10 mg TNBS in 50% ethanol). Forced swimming test (FST), pharmacological studies and tissues collection were performed 72 h following TNBS administration. To address a possible inflammatory origin for the behavior- al despair following colitis induction, tumor necrosis factor-alpha (TNF-α) level was measured in both the hippocampal and colonic tissue samples. In parallel, hippocampal inducible nitric oxide synthase (iNOS) and ni- trite level were evaluated. Pharmacological studies targeting the NO pathway were performed 30–60 min before behavioral test. Colitis was confirmed by increased colonic TNF-α level and microscopic score. Colitic mice dem- onstrated a significantly higher immobility time in the FST associated to a significant increase of hippocampal TNF-α, iNOS expression and nitrite content. Acute NOS inhibition using either Nω-nitro-L-arginine methyl ester (a non-specific NOS inhibitor) or aminoguanidine hydrochloride (a specific iNOS inhibitor) decreased the immobility time in colitic groups. Moreover, acute treatment with both NOS inhibitors decreased the TNF-α level and nitrite content in the hippocampal samples. This study suggests that the NO pathway may be involved in the behavioral effects in the mouse TNBS model of CD. These findings endow new insights into the gut-brain communication during the development of colonic inflammation, which may ultimately lead to improved ther- apeutic strategies to combat behavior changes associated with gastrointestinal disorders. © 2015 Published by Elsevier Inc. 1. Introduction Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic and relapsing intestinal disorders with complex pathogenesis (Molodecky et al., 2012). IBD is the most common and serious chronic inflammatory condition of the gastrointes- tinal tract (Molodecky et al., 2012). It is thought to arise secondary to a genetically determined susceptibility to inflammation in response to environmental triggers that have yet to be defined. The most common course of the disease is one of recurrent relapses. Several factors have been suggested to initiate the disease or relapses including behavioral dysregulation. Psychological needs of CD and UC patients need to be clearly ad- dressed, as emerging evidence point to an independent and important Progress in Neuro-Psychopharmacology & Biological Psychiatry 64 (2016) 131–141 Abbreviations: Alzheimer’s disease, (AD); Aminoguanidine hydrochloride, (AG); Analysis of variance, (ANOVA); Autonomic nervous sytem, (ANS); Bovine serum albumin, (BSA); Central nervous system, (CNS); Central nucleus of the amygdala, (CeA); Corticotropin-releasing factor, (CRF); Crohn’s disease, (CD); Dextran sulfate sodium, (DSS); Ethylenediaminetetraacetic acid, (EDTA); Forced swimming test, (FST); Inducible nitric oxide synthase, (iNOS); Inflammatory bowel diseases, (IBD); Intraperitoneal, (i.p.); Intrarectal, (i.r.); Lipopolysaccharide, (LPS); Myeloperoxidase, (MPO); Nitric oxide, (NO); Nω-nitro-L-arginine methyl ester, (L-NAME); Paraventricular nucleus of the hypothalamus, (PVN); Parkinson’s disease, (PD); Parvocellular part of paraventricular nucleus of the hypothalamus, (pPVN); Parkinson’s disease, (PD); Phenylmethylsulfonyl fluoride, (PMSF); Phosphate Buffered Saline, (PBS); Polyvinylidene fluoride, (PVDF); Sodium dodecyl sulfate, (SDS); Tumor necrosis factor-alpha, (TNF-α); Ulcerative colitis, (UC); Water-avoidance stress, (WAS); 2, 4, 6-trinitrobenzenesulfonic acid, (TNBS). ⁎ Corresponding author at: Departments of Immunology and Internal Medicine, Section of Gastroenterology, College of Medicine, University of Manitoba, 750 McDermot Avenue, Winnipeg, Manitoba R3E 0T5, Canada. E-mail address: jean-eric.ghia@umanitoba.ca (J.-E. Ghia). 1 These authors contributed equally in the study. http://dx.doi.org/10.1016/j.pnpbp.2015.08.004 0278-5846/© 2015 Published by Elsevier Inc. Contents lists available at ScienceDirect Progress in Neuro-Psychopharmacology & Biological Psychiatry journal homepage: www.elsevier.com/locate/pnp