Site of emetic action of oral copper sulfate in dogs. (II) Importance of lower duodenum.

Sensitivities of the stomach and duodenum to oral copper sulfate emesis were compared in dogs. 1) Dogs equipped with a stainless stell cannula in the middle of the duodenum were challenged to the oral threshold emetic dose of copper sulfate administered by a gastric tube. When the cannulas were opened, the oral thresholds were not effective to elicit vomiting in the most cases (1/13). Fairly rapid and high rate recoveries of copper through the open cannula were noted. With the closed cannulas, the thresholds were highly effective (16/16). 2)In the dogs with a cannula at the upper part of the jejunum, the oral threshold doses were always effective whether the canula was opened (9/9) or closed (11/11). Recovery rates of copper from the cannula were usually poor. 3) The oral thresholds administered into the proximal end or the middle of the duodenum through a PVC tubing were equally effective. 4) Although copper sulfate might irritate the stomach and upper duodenum to evoke vomiting, these results suggested a higher sensitivity of the lower duodenum.