Role of oxidative stress in animal model of visceral pain

Reactive oxygen species play an important role both in physiological and pathophysiological reactions. The aim of this study was to determine the role of free radicals and antioxidants in the development of visceral pain. Visceral pain was produced by colorectal distension (CRD) in adult rats. CRD was caused by insertion of a lubricated latex balloon into the descending colon and rectum followed by inflation to 80 mm Hg for 10 min. During CRD, visceral pain was rated on 0–3.5 point scale. Oxidative stress was determined indirectly by measurement of free radical scavenging enzymes (glutathione peroxidase (GPx) and superoxide dismutase (SOD)) in the blood, liver and brain. Following CRD we observed (1) all rats expressed signs of visceral pain (overall rating was 1.83), (2) SOD and GPx levels were increased in the liver and blood, and decreased in the brain samples and (3) administration of the antioxidant Trolox, a water-soluble derivate of vitamin E, prior to CRD, prevented SOD and GPx changes in the liver, blood and brain, but did not affect pain scores. It was concluded, that CRD as a model of visceral pain, increases oxidative stress in animals, which could be prevented by prior administration of antioxidants; however, antioxidants did not attenuate signs of visceral pain caused by CRD.