Excitatory and Inhibitory Effects of Vagus Stimulation on Gastric Motility in the Cat

Abstract

Abstract In acute experiments on cats gastric motor responses were recorded during vagal stimulation with a constant frequency but with different values of impulse duration and voltage. With very low values cardiac responses only were obtained. With higher values pure excitatory motor effects of the stomach were elicited, but when the values were increased above a certain point a gradual depression of the response was observed. After atropine, the gastric motor responses were abolished, and pure relaxation was the result of stimulations which previously had given rise to partially depressed excitatory responses. It is suggested that two groups of efferent fibres, influencing gastric motility are present in the vagus nerve. According to the strength‐duration diagram both fibre groups are of smaller caliber than the cardioinhibitory fibres, the inhibitory fibres being the thinnest ones. The excitatory fibres appear to be cholinergic, whereas the inhibitory effect seems to be mediated by some other transmitter substance.