A Rat Model of Chronic Postinflammatory Visceral Pain Induced by Deoxycholic Acid

Background & Aims: Chronic visceral hyperalgesia is considered an important pathophysiologic symptom in irritable bowel syndrome (IBS); previous gastrointestinal inflammation is a potent etiologic factor for developing IBS. Although there are several animal models of adult visceral hypersensitivity after neonatal perturbation or acute colonic irritation/inflammation, current models of postinflammatory chronic visceral hyperalgesia are unsatisfactory. The aim of this study was to establish a model of chronic visceral hyperalgesia after colonic inflammation in the rat. Methods: Deoxycholic acid (DCA) was instilled into the rat colon daily for 3 days and animals were tested for up to 4 weeks. Results: DCA induced mild, transient colonic inflammation within 3 days that resolved within 3 weeks. An exaggerated visceromotor response, referred pain to mechanical stimulation, increased spinal Fos expression, and colonic afferent and dorsal horn neuron activity were apparent by 1 week and persisted for at least 4 weeks, indicating chronic dorsal horn hyperexcitability and visceral hyperalgesia. There was no spontaneous pain, based on open field behavior. There was a significant increase in opioid-receptor activity. Conclusions: DCA induces mild, transient colitis, resulting in persistent visceral hyperalgesia and referred pain in rats, modeling some aspects of postinflammatory IBS.