Copper Sulphate Emesis: A Study of Afferent Pathways from the Gastrointestinal Tract1

V OMITING is a complicated act which involves the coordinated activities of many motor systems of the body including both the somatic and autonomic nervous outflows. The orderly sequential action of the different muscle groups used in emesis has been clearly demonstrated by the now classical work of Cannon (I). Equally complex is the question of the sensory pathways of vomiting. The roles of the numerous afferents investigated by various workers on this problem are not in agreement. Our investigation concerns the essential sensory pathways for emesis arising from the gastrointestinal tract. Miller (2) studied the afferent nerves in the emetic action of mustard, and concluded that the vagi alone were responsible for this function, since immediately following vagotomy emesis was no longer elicitable; this was not the case after section of the splanchnic nerves. The importance of afferents in the vagus was further stressed by Bayliss (3) who produced vomiting by intraperitoneal injection of staphylococcus enterotoxin and found that emesis rarely occurred following division of the vagi in the acute preparation. Goldberg (4) induced vomiting by distending an isolated pyloric pouch and found that this reflex also disappeared after vagotomy. On the other hand, many workers (5) observed that vagotomy did not interfere with vomiting in man. In addition, Walton, Moore and Graham (6) reported that in order to prevent the vomiting of experimental peritonitis, they had to section both the vagi and the splanchnic nerves. The present report represents the results of a corollary study made during the course of experimental work on the vomiting center (7), in which a considerable quantity of data were amassed on the action of copper sulphate in the elicitation of emesis. This information affords the opportunity for evaluating the relative importance of the various visceral afferent components in vomiting arising from the gastrointestinal tract, and in addition, has uncovered other emetic properties of copper sulphate.