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