CAPSAICIN-LIKE EFFECT OF RESINIFERATOXIN IN THE RAT STOMACH

Neurochemical and functional studies were performed to investigate and to compare the effects of resiniferatoxin and capsaicin in the rat st omach. Neonatal administration of resiniferatoxin (0.6-1.6 mumol/kg su bcutaneously (s.c.)) produced a marked decrease in gastric calcitonin gene-related peptide-like immunoreactivity in both secretory and non-s ecretory region of the stomach. Almost complete depletion of the pepti de was determined by neonatal administration of capsaicin (164 mumol/k g s.c.). Vasoactive intestinal polypeptide-like immunoreactivity was c oncomitantly unaffected by resiniferatoxin or capsaicin, thus showing the selectivity of action of the neurotoxins on gastric afferent fiber s. Oral administration of an equimolar dose (0.3 nmol/kg) of resinifer atoxin or capsaicin together with 50% ethanol reduced at a similar ext ent gastric haemorrhagic lesions produced by the mucosal barrier-break er agent. These findings provide evidence that resiniferatoxin and cap saicin may act on a common neuronal target in the rat stomach and that the acute exciting (protective) effect is of the same magnitude.