Does a single exposure to social defeat render rats more vulnerable to chemically induced colitis than brief inescapable foot-shocks?

Abstract

All social species are to different degrees exposed to stressors being physical or social environmental, which may affect health and well-being. Stressful and traumatic situations have direct effect on immune responses that may underlie susceptibility of developing somatic illness. In animal research, different types of stressors have been investigated in studying the effect on bowel disorders, some stressor being more or less of environmental origin. We aimed therefore to explore whether a more natural stressor would differ from a stressor of more unnatural characteristics on dextran sulphate sodium (DSS) induced colitis in adult rats. Specifically, if social stress within a single social defeat (SD) paradigm would be a more potent stressor than brief inescapable foot-shocks (IFS) in causing elevated faecal granulocyte marker protein (GMP), crypt- and inflammation score in colon tissue. Three groups of male Wistar rats were used; socially defeated rats; inescapable foot-shock rats; and comparison rats. Main findings showed no difference between the groups on GMP levels, however, there was a significant difference on inflammation and crypt score for the distal part of colon, detected through histology, where socially defeated rats were more susceptible. A single SD seems to be more adverse for these animals, but further studies are recommended to validate a broader range of different outcomes comparing two such different rodent stress models.