Capsaicin-induced release of substance P-like immunoreactivity from the guinea pig stomach in vitro and in vivo.

Capsaicin induced a release of substance P-like immunoreactivity (SP-LI) in superfusates from gastric fundic mucosa of guinea pig in vitro and from gastric perfusates of anaesthetized guinea pigs in vivo. Tissue SP-LI from the gastric fundus was reduced (43.4%) by systemic capsaicin desensitization. These findings provide direct neurochemical evidence which supports the hypothesis for the involvement of local neuropeptide release in the 'gastric defence mechanism' played by capsaicin-sensitive nerves.