Inflammation of the colonic wall induced by formalin as a model of acute visceral pain

Pain. 1994 Jun;57(3):327-334. doi: 10.1016/0304-3959(94)90008-6.


Acute inflammation of the sigmoid wall was induced by perendoscopic injection of formalin (50 microliters, 5%) under brief anesthesia in rats. The procedure was followed by behavioral patterns that significantly differed from those in animals injected with isotonic saline instead of formalin. Analysis of the formalin-induced behaviors allowed for the calculation of a pain score that evolved in a biphasic manner along the 3 h of test. The score was dose-dependently reduced by morphine (0.5-4 mg/kg), and the analgesic effect of the largest morphine dose was abolished by naloxone (2.4 mg/kg). These results suggest that formalin into the sigmoid colon is a new model of visceral pain, presumably through direct irritation at injection site and/or localized acute inflammation of the intestinal wall.

MeSH terms

  • Acute Disease
  • Animals
  • Colitis / chemically induced*
  • Colitis / physiopathology
  • Disease Models, Animal
  • Female
  • Formaldehyde*
  • Morphine / therapeutic use
  • Naloxone / therapeutic use
  • Pain Measurement
  • Pain* / physiopathology
  • Palliative Care
  • Rats
  • Rats, Sprague-Dawley
  • Sodium Chloride
  • Viscera*


  • Formaldehyde
  • Naloxone
  • Sodium Chloride
  • Morphine