Relation between cholecystokinin and antral innervation in the control of gastric emptying in the rat

Abstract

Background - Antral motility and the hormone cholecystokinin (CCK) are major determinants of the rate of gastric emptying. The relation between CCK and antral neurons in regulating gastric emptying is uncertain. Benzalkonium chloride (BAG) causes selective lesions in gut myenteric neurons after serosal application Aim - To develop a model of antral denervation using BAG to enable the study of the relation between GCK and antral neurons in regulating gastric emptying. Methods - BAC, vehicle or the afferent neurotoxin capsaicin were applied to the serosal surface of the rat antrum or corpus; neurochemical markers of intrinsic and afferent neurons were detected by using immunohistochemistry and radioimmunoassay. Gastric retention of solids was determined after fasting, and emptying of liquids was measured in rats with gastric fistulae. Results - In BAC treated rats radioimmunoassay of tissue extracts revealed a dose related specific loss of gastrin releasing peptide, substance P, and vasoactive intestinal polypeptide immunoreactivities from the treated region, and immunohistochemistry revealed loss of the neuronal marker PGP 9.5 and the afferent neuropeptide calcitonin gene related peptide (CGRP). Adjacent untreated regions were unaffected by BAG, with the exception that CGRP was depleted in both corpus and antrum after antral treatment. After antral BAG treatment fasted rats retained solids for over 48 hours. Moreover, in antrally denervated rats with gastric fistulae, the emptying of saline, acid and peptone was delayed substantially. The CCK dependent inhibition of gastric emptying of peptone was preserved after antral treatment with BAG. Conclusion - Serosal BAG causes lesions in the innervation of the treated region of the stomach. The innervation of the antrum is essential for normal emptying of both liquids and solids, but the inhibition of gastric emptying produced by GCK is not dependent on antral neurons.