Background: Sensory neurons have been proposed to play a critical role in the protection of the gastric mucosa from a variety of necrotizing agents. The purposes of this study were (1) to investigate the effect of topical capsaicin, a sensory neuron stimulant, on the gastric mucosal injury caused by the topical application of low concentrations of bile acid and (2) to determine whether local neuronal blockade with topical lidocaine or cyclooxygenase blockade with systemic indomethacin has any effect during pretreatment with capsaicin.
Methods: Before injury with topical 5 mmol/L acidified taurocholate (pH 1.2) rat stomachs were pretreated with either vehicle or capsaicin (160 mmol/L), both with and without prior administration of either lidocaine (1%) or indomethacin (5 mg/kg subcutaneously). Injury was assessed by measuring net transmucosal ion fluxes, the appearance of deoxyribonucleic acid into the gastric lumen, and gross and histologic injury scores.
Results: Pretreatment with topical capsaicin significantly (p < 0.05) decreased bile acid-induced net luminal ion fluxes and luminal deoxyribonucleic acid accumulation, an effect blocked by both lidocaine and indomethacin.
Conclusions: Thus both local neuronal blockade and cyclooxygenase inhibition block the protective effect of capsaicin, findings corroborated by gross and histologic injury analysis. This study suggests that sensory neurons may mediate gastric mucosal protection from bile acid injury by increasing synthesis of endogenous prostaglandins.