The effects of glucagon and secretin on food- or morphine-induced motor activity of the distal colon, rectum, and internal anal sphincter were investigated in 12 healthy subjects. Intraluminal pressure changes were measured using a triple-lumen polyvinyl tube assembly with 3 side orifices. Glucagon, administered intravenously, caused significant inhibition of food- or morphine-induced motor activity of both the distal colon and rectum. In contrast, secretin did not suppress morphine-induced motor activity but did significantly inhibit food-stimulated motor activity of the distal colon. The inhibitory effect of secretin on motor activity of the rectum was insignificant. Morphine, but not food, elevated the pressure of the anal sphincter which was not effected by glucagon or secretin. Hyperglycemia, produced by the infusion of 5% glucose, had no effect on motor activity. These studies demonstrate that glucagon but not secretin, in the doses employed, inhibits morphine-induced motor wave activity of both the distal colon and rectum and that this inhibitory effect is not secondary to hyperglycemia. Furthermore, the rise in anal sphincter pressure is not affected by glucagon or secretin.

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