Effect of epinephrine on relation of acetylcholine to intestinal tonus

¹ Department of Physiology, University of Wisconsin Medical School, Madison, Wisconsin

Isolated segments of rabbit intestine were subjected to epinephrine in order to depress intestinal tonus. The acetylcholine concentration of the fluid surrounding the rabbit intestine was assayed on guinea pig ileum which had been pretreated with dichlorophenyl-2-isopropylaminoethanol which blocked the action of epinephrine on the ileum without altering the response to acetylcholine. In the 21 tests performed, acetylcholine concentration of the rabbit bath fluid was found to be directly proportional to intestinal tonus. This indicates that epinephrine influences intestinal tonus indirectly through its ability to alter acetylcholine metabolism. Statistical tests showed that these data could be combined with data from earlier experiments in which it was found that acetylcholine concentration is directly proportional to the tonus of spontaneously contracting isolated intestinal segments. It is therefore concluded that both under control conditions and in the presence of epinephrine, acetylcholine is the principal factor responsible for the regulation of tonus in isolated intestinal segments.