Increase of growth-associated protein-43 immunoreactivity following cyclophosphamide-induced cystitis in rats.

We examined the effect of inflammation on immunoreactivity of growth-associated protein (GAP-43) in the rat urinary bladder in which acute cystitis was induced with cyclophosphamide (CPA). Following CPA injection, the number of GAP-43 labeled nerves was significantly increased in the muscle layer. Immunoreactivity of PGP9.5, which was used as an axonal marker, was not augmented following CPA injection. Double fluorescence immunohistochemistry revealed that substance P immunoreactivity was present in most GAP-43 immunoreactive fibers (90.2%) in the inflamed bladder. Electron microscopic examination showed that GAP-43 immunoreactivity was localized on axons. Some GAP-43 positive axons showed degeneration. Possible significance of the increase of GAP-43 immunoreactive afferent nerve fibers in the muscle layer of acutely inflamed bladder was discussed.