The effect of stimulation of the vagi on the pyloric region of the stomach

Abstract

THE course taken by the vagus fibres which supply the pyloric region has not been very definitely ascertained. Anatomically the main branches of the anterior and posterior vagal trunks from the cesophageal plexus are traceable to the region of the incisura angularis and their terminal fibres supply the pyloric antrum. In no instance does the anterior or posterior vagal trunk send fibres as far as the pylorus canal or sphincter. Many observers state, however, that all the pyloric region receives its nerve supply from these branches. The anterior vagal trunk has been show-n to give off a branch, and sometimes two or three branches, to the liver, which communicate with sympathetic fibres and have been called the hepatic branch of the vagus. From these, nerve strands descend to supply the pylorus and first part of the duodenum. La tarj et(1) states that the pylorus receives its entire nerve supply, in man and the dog, from above and considers these strands to consist wholly of sympathetic fibres. One of us, McCrea (2), has dissected the hepatic branch in man, dog, cat and rabbit and shown that the strands given off to the pylorus contain vagus fibres. It seemed then desirable to ascertain the effects which this pyloric branch is capable of producing upon the musculature of the pyloric region.In a recent paper, McCrea, McSwiney and Stopford(3), working on the intact stomach, have shown that stimulation of the vagi influences both the motor activity and "postural tonus," the type of reaction depending on the condition of the peripheral mechanism. The entogastric pressure was used as an indication of the state of activity of the peripheral mechanism, as this was found to vary with the degree of contraction of the viscus on its contents. In the passive organ (obtained by starving an animal for at least 12 hours) which did not normally maintain an entogastric pressure, stimulation of the nerve caused an augmentor response. In the active stomach (obtained by feeding a starved animal

The cardiac sphincter in the cat

“…Mixed effects on vagal stimulation were only seen at low frequencies and may have been due either to the inclusion of a few muscle fibres from the stomach or oesophagus (which are contracted by vagal stimulation) or to a mixture of adrenergic and cholinergic nerves in the vagus, as suggested by Paton and Vane (1956). Either interpretation would be in accord with the views of McCrea et al (1925), who found that the effect of vagal stimulation was dependent upon the resting tone of the sphincter. In a muscle with a low tonus, excitatory effects would show up best, but if the muscle is already contracted relaxation would predominate.…”

“…The reactions of this last 2 cm. were also different from those of the body of the oesophagus and from those of the stomach, so that it cannot be said to behave as part of the gastric musculature as suggested by Carlson et al (1922) and by McCrea et al (1925). The region of the sphincter comprises a longitudinal and circular muscle coat with mucous membrane containing the finely distributed muscularis mucosa.…”

“…Nor is there general agreement on the effects brought about by stimulation of the extrinsic nerve supply to the region, although they have been repeatedly studied (Langley, 1898;May, 1904;Klee, 1919;Koennecke, 1922;Veach, 1925Veach, , 1926. Some experiments have suggested that the response of the sphincter is dependent upon the coexisting gastric tonus (Carlson et al, 1922;McCrea, McSwiney, and Stopford, 1925).…”

Further observations on the reaction of smooth muscle to the H‐ion concentration

“…On decreasing the pH a grouping of contractions was frequently observed in the region of pH 7.1. We have termed the condition "spasm " 150 owing to the similarity of the tracings to those obtained by Mc Crea and McSwiney (6). These observers in recording the movements of the pyloric antrum on stimulation of the peripheral end of the vagus nerve found that " a strong stimulus may cause a sustained contraction, the rhythmic movements increasing in rate and starting above the base line indicating summation."…”

The sympathetic innervation of the stomach

“…Inhibition of movement of the pyloric antrum is independent of a rise of bloodpressure, and takes place when motor responses are observed in the body of the stomach. Moreover, McCrea and MacDonald [1928] point out that the inhibitory effect of adrenaline on the stomach is well shown in doses which produce a fall in blood-pressure, whereas the motor effect is most frequently obtained with large doses when there is a very great rise of blood-pressure. McCrea and McSwiney [1928] have shown that splanchnic stimulation can cause contraction of the stomach during compression of the thoracic aorta.…”