The Reversal of Action of Ergotamine by Calcium and Changes in C H

Abstract

As stated in the preceding communication, 1 the response of the intestine to ergotamine has been studied in different animals. No observations have been made, however, to determine whether changes in ionic content of the surrounding medium modified the action of ergotamine. We, therefore, undertook the investigation of this problem and selected the intestine of the rat for the test object. As far as we know, no studies with ergotamine on the intestine of this animal have been reported. The experiments of Rosenmann, 2 however, are of interest in this connection. He observed that ergotoxin produced stimulation in the isolated intestine of the rat.

Our experiments were carried out by means of the Magnus method, segments of different parts of the intestine being suspended in oxygenated Locke solution maintained at almost uniform temperature, usually 37.5° C. The variations which sometimes occurred seldom exceeded 0.2° C. We found that concentrations of 1:100,000 and sometimes 1:1,000,000 ergotamine in Locke solution with a pH of about 7.2 or 7.3 and containing 0.014% calcium chloride, produced a considerable decrease of tonus, the relaxation being more marked in the ileum and colon than in the duodenum. The rhythmic movements, however, were usually stimulated, especially the amplitude. When the amount of calcium in the solution was increased to 0.028 or 0.056% a striking change in the action of ergotamine occurred when the H-ion concentration was decreased below neutrality, especially when it was around pH of 6.5. The same amounts of ergotamine now caused a very marked increase of tonus which occurred within a few seconds after it was added to the solution. The duration of the effect varied in different experiments, but it usually lasted several minutes or longer.