Capsaicin-sensitive mechanisms and experimentally induced duodenal ulcers in rats.

The incidence and degree of cysteamine- or dulcerozine-induced duodenal ulcers are increased by systemic capsaicin desensitization (50 mg kg-1 s.c. 4 days before) in adult rats. Acute administration of capsaicin, but not neurokinins or CGRP, produced a small but distinct plasma extravasation (Evans blue leakage) in the rat proximal duodenum which was absent in capsaicin-pretreated rats. These findings indicate the existence of a capsaicin-sensitive 'duodenal defence mechanism' in rats.