Action of Morphine Sulphate on Intestinal Motility and its Modification by Atropine Sulphate

Abstract

The experiments were conducted on unanesthetized female dogs with weights ranging between 12-18 kg. Two Thiery Vella loops of adjacent parts of the ileum were prepared, which enabled us to record, in the same dog simultaneously, changes in tone, rhythmic and peristaltic movements in one loop by the balloon method, 1 and the actual propulsive activity in the second loop. For the latter purpose the method of Quigley, Highstone and Ivy was followed; the bolus used was made of rubber crepe of fine quality soaked in liquid paraffin. 2

Morphine sulphate in doses of 1 mg. per kilo injected subcutan-eously causes an increase in tone, diminishes segmentary movements and abolishes peristaltic waves. This confirms the results of the experiments of Plant and Miller. 3

The propulsive activity after this dose of morphine is at first increased and this initial increase in the speed of propulsion is later followed by a marked decrease. While the normal time for a bolus to pass through an intestinal loop of 9-10 cm. in length varied between 6-12 minutes, the same distance was covered within 20-40 seconds after morphine. The period of increased speed of propulsion started within 1-2 minutes after the morphine-injection and lasted for an average of 20-40 minutes. After that the speed of propulsion changed abruptly, becoming“ much slower than normal; the latter condition lasting for about an hour.

While these results agree in general with those of Quigley, High-stone and Ivy 4 they differ in details. In our experiments the duration of the period of increased propulsive activity was longer and the maximal speed of propulsion was greater.

According to Plant and Miller 3 atropine sulphate in doses sufficient to paralyze the vagus (0.2 mg. per kilo subcutaneously) has no apparent influence on the effect of morphine sulphate on tone, seg-mentary and peristaltic movements of an intestinal loop of the ileum in a Thiery Vella dog (recorded with the balloon method).

Gruber, Greene, Drayer, and Crawford, however, found that the increased tone caused by morphine could be antagonized completely by a following injection of atropine. They gave in one of their 2 experiments one mg. and in the other 1.4 mg. of morphine sulphate per kilo intravenously, followed by 0.5 mg. and 0.35 mg. respectively of atropine sulphate intravenously. 5

In dogs with 2 Thiery Vella loops atropine in a dose of 0.2 mg. per kilo subcutaneously, which was found to abolish the inhibitory influence of the vagus on the heart, invariably abolished the increased rate of propulsive activity produced by morphine. The intestinal effect always coincided with the increasing effect of atropine on the heart. Atropine given before morphine prevented the increase in propulsive activity which invariably followed morphine alone.

Our results,∗ using the same dose and method of administration as Plant and Miller, confirm their findings in that atropine does not have any apparent influence upon tone, segmentary and peristaltic movements altered by morphine. Larger doses of atropine, however, given subcutaneously and the same or larger doses given intravenously antagonized the effect of morphine in a way similar to the results of Gruber, et al.