Mechanisms of referred visceral pain: uterine inflammation in the adult virgin rat results in neurogenic plasma extravasation in the skin.

The purpose of this study was to investigate the mechanisms of referred pain observed in female patients with pain from the reproductive organs. We developed a model of inflammatory uterine pain in the rat. Inflammation of the uterus in rats pretreated with Evans Blue Dye resulted in dye extravasation in the skin over the abdomen, groin, lower back, thighs, perineal area and proximal tail, thus providing for the first time evidence for the trophic changes observed in the area of referred visceral pain in an animal model of uterine pain. The neuronal pathways mediating the observed dye extravasation in the skin after uterine inflammation may include dichotomizing afferent fibers, afferent-afferent interactions via a spinal cord pathway or a sympathetic reflex. This model will allow to gain further insight into the mechanisms of referred pain and the trophic changes observed in the area of referred pain in visceral disease.