Abstract
The studies of Hatcher and Weiss 1 and of Koppanyi 2 suggested the presence of a medullary defecation center, or at any rate, the existence of a non-peripheral control of defecation.
Investigating the gastro-intestinal actions of graded doses of ergotamine tartrate in intact, unanesthetized dogs and cats, we observed certain facts which further support the assumption of a central control of defecation.
Dogs and cats strain and defecate rather promptly following small or moderate intravenous doses of ergotamine tartrate. Doses are given in mgm. × kilogram body weight. In the dog doses of 0.02-0.2 mg. produced prompt and repeated straining and defecation, whereas doses of 0.5 mg. or above were effective only after a considerable delay. (10 min.) In cats, doses of 0.01 and 0.015 mg. also produced straining and defecation whereas doses of 0.1 mg. or higher either produced no defecation or a very delayed response (9-68 min.). Thus in cats the optimum effective doses are somewhat smaller than in dogs. It is also to be noted that there is a close correlation between the evacuation and emetic response produced by ergotamine tartrate. In practically every case where vomiting was produced, defecation also took place and when vomiting did not take place the animals either failed to defecate or evacuation ensued after considerable delay (peripheral effects?).
In 2 dogs we failed to produce defecation by application of ergotamine tartrate (0.03 mg.) on the floor of the fourth ventricle; but the application of larger doses (0.2 mg.) upon the floor inhibited the usual evacuation following optimum intravenous doses. Similarly, the subcutaneous injection of 20 mg. of morphine sulphate eliciting the usual immediate evacuant response, inhibited the evacuant effects of subsequent intravenous doses of 0.1 mg. of ergotamine tartrate.
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