A role for calcitonin gene-related peptide in protection against gastric ulceration

Objective: The goal of this investigation was to determine the role of calcitonin gene-related peptide (CGRP) in gastric mucosal resistance to ulceration. Summary Background Data: CGRP is a 37-amino acid peptide found in the peripheral ends of afferent gastric neurons. CGRP is known to inhibit acid secretion, stimulate mucosal blood flow, and stimulate release of somatostatin. Methods: The release of CGRP in response to intragastric and intra-arterial administration of capsaicin in the isolated, vascularly perfused rat stomach was measured by radioimmunoassay. The molecular forms of CGRP released were analyzed by gel filtration chromatography. The effect of intravenous CGRP or intragastric capsaicin on gastric ulceration induced by 100 mmol/L HCl and indomethacin was studied in intact and endogenous CGRP- depleted rats. Results: Intra-arterial capsaicin (concentration range, 10^{- 7} to 10^-5 mol/L) stimulated a prompt and sustained release of immunoreactive CGRP, of which 84% coeluted with rat 1-37 CGRP I by gel filtration. Intragastric capsaicin (range, 10^-5 to 10^-4 mol/L) failed to release CGRP into the vascular perfusate. In intact rats, intragastric capsaicin (10^-6 mol/L) or intravenous CGRP I (10 μg/kg/hr) reduced the number and area of mucosal lesions caused by HCl and indomethacin compared with the findings in control rats. Rats depleted of endogenous CGRP were more susceptible to gastric ulceration than were normal rats. Intragastric capsaicin failed to protect the mucosa of CGRP-depleted rats, whereas exogenous intravenous CGRP was effective. Conclusions: These data support the hypothesis that CGRP released from gastric enteric neurons mediates gastric mucosal resistance to ulceration by noxious agents.