Our objective was to study the mechanism of action of gastrin and histamin H2 receptor antagonist on the motility of the gastrointestinal area.
In each of 12 mongrel dogs, eight bipolar electromyograms were obtained from the antrum of the stomach to the ileum on serosal surface, and in nine dogs undergoing that the small intestine was transected 20 cm from the ligament of Treitz.
The effects of tetragastrin (1.0-10.0μg·kg-1·h-1) were studied against the presence of atropine, cimetidine and d-chlorpheniramine maleate.
The frequency of electrical control activity (ECA) along the canine small intestine, and changes in ECAs frequency were studied normal and following upper small intestinal transection. In intact, the frequency of ECAs gradient decreased aborally in a stepwise fashion in normal intestine. Although the gradient was markedly reduced or even abolished distal to the level of transection, an intrinsic ECAs frequency gradient was demonstrated, it remained at a low level indefinitely. The normal ECA pattern and its alterations following transection were significantly influenced by tetragastrin.
The act of tetragastrin in a dose of 1.0 to 5.0μg·kg-1·h-1 had not statistically effect on ECAs frequency and its dysrhythmias, and it did cause a small increase in the frequency of ECA at the antrum, whereas, with the highest dose (10.0μg·kg-1·h-1) of used, the increase of mean frequency of ECA in the distal portion to the line of transection, in particular, was significantly greater compared to the change in the proximal portion.
It was only cimetidine (8.0 mg·kg-1) that antagonized this action of tetragastin (10.0μg·kg-1·h-1). Histamine H2 receptors are suspected of being associated with the action the gastrin has of enhancing ECAs frequency.
The results of this study indicate that histamine H2 receptors regularize gastrointestinal ECAs frequency.
