Acid-sensitive and alkaline-sensitive sensory neurons regulate pH dependent gastrin secretion in rat

We examined the role of capsaicin-sensitive afferent neurons in pH-dependent gastrin secretion in the rat stomach. The change in serum gastrin levels relative to changes in luminal pH (using omeprazole for luminal alkalization or 0.1 N HCl for luminal acidification) was studied after oral administration of 4% lidocaine or capsaicin-induced ablation of afferent neurons. The increase of serum gastrin levels by luminal alkalization was significantly inhibited (50%) after administration of 4% lidocaine. Capsaicin pretreatment (125 mg/kg subcutaneously over two days) inhibited the change in serum gastrin levels both the luminal alkalization (38%) and acidification (66%). Antral gastrin contents, somatostatin contents, gastrin mRNA expression, and somatostatin mRNA expression were not significantly affected by capsaicin pretreatment. Our results indicate that capsaicin-sensitive afferent neurons participate in the secretion of gastrin by luminal alkalization and inhibition of gastrin by luminal acidification.