Degeneration of axons in the ureteric and duodenal nerve plexuses of the adult rat following in vivo treatment with capsaicin.

The fine structure of the ureteric and duodenal nerve plexuses was studied in specimens taken from adult rats 24 h after subcutaneous injection of 50 mg/kg capsaicin and in specimens taken from rats injected with the vehicle used to emulsify the capsaicin. In specimens from capsaicin-treated rats, there was extensive degeneration of axons in the ureteric plexuses and widespread, but much smaller amounts of degeneration of axons in the duodenal plexuses. Comparison of the fine structure of the plexuses in the capsaicin-treated rats with that of the plexuses in the control rats indicated that the degeneration was confined to axons with terminals containing mainly large dense-cored vesicles.