THE EFFECTS OF 5-HYDROXYTRYPTAMINE UPON THE INTESTINAL MOTILITY, ESPECIALLY WITH RESPECT TO THE INTESTINAL MUCOSAL INTRINSIC REFLEX

Abstract

1) Recording the motility of as well as the fluid transport through the denervated dog's jejunal loop the effects of 5-HT and additionally of some chemical substances upon the intestinal motility were studied.2) When 5-HT was applied to the mucosal or serosal surface, the intestinal motility was excited above and inhibited below the stimulated spot. The removal of the villi did not change the responses at all. However, no response was observed after cauterizing the superficial layer of the basal part of the mucosa, tunica propria surrounding the crypts.3) The reflex responses did not appear, when the application of 5-HT to the mucosal surface was preceded by that of C6 or tetraethylammonium bromide.4) After cocainization of the mucosal surface the responses described above were not produced by stroking, or applying HCl to the mucosa, whereas they were rarely so by applying 5-HT to the same spot as before.5) When 5-HT was repeatedly applied at a short interval of time to the one and the same spot of the mucosa, the responses grew weaker and weaker, disappearing finally (5-HT insensitivity). In-this case, however, stroking, or applying HCl to the mucosa produced the responses.6) 5-HT acted upon the intestine at first to allow the fluid transport through it to be retarded and then to become insensitive to the subsequent application of 5-HT; in this instance HCl solution, however, produces a remarkable retardation of flow.7) From the results described above it may be said that 5-HT acts upon the peripheral nerve endings which are presumed to be distributed to the superficial layer of the basal part of the mucosa, tunica propria surrounding the crypts.8) Phenyldiguanide (PDG), as far as the mucosal intrinsic reflex is concerned, behaves exactly identical with 5-HT.