Inflammation of the colonic wall induced by formalin as a model of acute visceral pain
Marcel Miampamba1, Sylviane Chéry-Croze, Fabien Gorry
1INSERM Unité de Recherches de Physiopathologie Digestive (U45), Pavilion H bis, France URA CNRS 1447 Laboratoire de Physiologie Sensorielle, Audition et voix, Pavilion U France Service d'Anatomie Pathologique, Hôpital Edouard Herriot, 69437 Lyon cedex 03 France.
Abstract:
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.
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