Growth of nerve fibres into murine peritoneal adhesions

Adhesions in the peritoneal cavity have been implicated in the cause of int estinal obstruction and infertility, but their role in the aetiology of chr onic pelvic pain is unclear. Nerves have been demonstrated in human pelvic adhesions, but the presence of pain-conducting fibres has not been establis hed. The purpose of this study was to use an animal model to examine the gr owth of nerves during adhesion formation at various times following injury and to characterize the types of fibres present. Adhesions were generated i n mice by injuring the surface of the caecum and adjacent abdominal wall, w ith apposition. At 1-8 weeks post-surgery; adhesions were processed and ner ve fibres characterized histologically, immunohistochemically, and ultrastr ucturally. Peritoneal adhesions had consistently formed by 1 week after sur gery and from 2 weeks onwards, all adhesions contained some nerve fibres wh ich were synaptophysin, calcitonin gene-related peptide, and substance P-im munoreactive. and were seen to originate from the caecum. By 4 weeks postsu rgery, nerve fibres were found to originate from both the caecum and the ab dominal wall, and as demonstrated by acetylcholinesterase histochemistry, m any traversed the entire adhesion. Ultrastructural analysis showed both mye linated and non-myelinated nerve fibres within the adhesion. This study pro vides the first direct evidence for the growth of sensory nerve fibres with in abdominal visceral adhesions in a murine model and suggests that there m ay be nerve fibres involved in the conduction of pain stimuli. Copyright (C ) 2000 John Wiley & Suns, Ltd.