A Pharmacological Study of the Inhibitory Mesenteric Nerves to the Intestine. ∗

An attempt to understand better some of the actions of cocaine, ephedrine and other drugs on the intestine, led to the use of the excised nerve-muscle preparation of the intestine described by Thomas. 1 At the time our experiments were begun, McSwiney and Robson 2 had reported the use of a similar preparation of the stomach, and since then there have appeared papers by Finkelmann 3 and McSwiney and Robson, 4 describing results with the nerve-muscle preparation of the intestine. Our results in general confirm those of the authors mentioned, and extend the study further.

A modified Locke solution was used to immerse the tissues, which were removed as required from rabbits and dogs anesthetized with urethane and chloretone or with amytal. Records were made of the movements of only the longitudinal muscle fibres. Stimulation of the mesenteric nerves was by means of the Harvard induc-torium, through platinum electrodes applied to the periarterial nerves. Slowly repeated shocks (1 to 10 per second), as well as rapid shocks (12 to 60 per second), and minimal effective as well as supermaximal strength, stimulating for periods up to 1 minute, resulted only in decrease in tone and inhibition of the movements of the intestinal muscle. The inhibition persisted for several seconds after stimulation ceased, and in a few instances, there was over-recovery of tone, with gradual return to normal, thus confirming the results of Thomas 1 All effects of nerve stimulation were closely imitated by epinephrine on each individual preparation. In no instance did a primary augmentation of intestinal activity result from nerve stimulation.

The inhibition was not prevented by nicotine or atropine in 1:10,000 concentration, or by a mixture of nicotine and atropine, each 1:10,000.