Chronic psychosocial stress induces visceral hyperalgesia in mice

Experimental and clinical evidence has shown that chronic stress plays an important role in the onset and/or exacerbation of symptoms of functional gastrointestinal disorders. Here, we aimed to investigate whether exposure to a chronic and temporally unpredictable psychosocial stressor alters visceral and somatic nociception as well as anxiety-related behaviour. In male C57BL/6J mice, chronic stress was induced by repeated exposure to social defeat (SD, 2 h) and overcrowding (OC, 24 h) during 19 consecutive days. Visceral and somatic nociception was evaluated by colorectal distension and a hot plate, respectively. The social interaction test was used to assess social anxiety. Mice exposed to psychosocial stress developed visceral hyperalgesia and somatic hypoalgesia 24 h following the last stress session. SD/OC mice also exhibited social anxiety-like behaviour. All these changes were also associated with physiological alterations, measured as a decreased faecal pellet output and hypothalamic-pituitary-adrenal (HPA) axis disruption. Taken together, these data confirm that this mouse model of chronic psychosocial stress may be useful for studies on the pathophysiological mechanisms underlying such stress-associated disorders and to further test potential therapies.