Influence of nitric oxide on histamine and carbachol – induced gastric acid secretion in the common African toad – Bufo regularis

Abstract

The study aimed to determine the influence of nitric oxide (NO) on the action of histamine and carbachol on acid secretion in the common African toad – Bufo regularis. Gastric acidity was determined by titration method. The acid secretion was determined when nitric oxide was absent following administration of NO synthase inhibitor; N-nitro-L-arginine methyl ester (L-NAME) and when nitric oxide was in excess by administration of exogenous NO donor, sodium nitroprusside (SNP). Histamine or carbachol increased acid secretion in the toad. Acid output increased from 0.32 ± 0.04 mEq/15min to 0.56 ± 0.08 and 0.61 ± 0.05 mEq/15min for histamine and carbachol respectively (P < 0.05). Pretreatment of the toad with L-NAME produced further increases in histamine (0.62 ± 0.06 mEq/15min) or carbachol (0.74 ± 0.06 mEq/15min) induced acid secretion respectively. SNP however, completely abolished the acid secretion stimulated by either histamine or carbachol. It was therefore concluded that nitric oxide has a negative influence on the histamine or carbachol – stimulated acid secretion in the toad – Bufo regularis.

Keywords: nitric oxide, histamine, carbachol, acid secretion

Nigerian Journal of Physiological Sciences Vol. 20(1&2) 2005: 74-78