The Myenteric Reflex as Exhibited by the Exteriorized Colon of the Dog

A pharmacological analysis of the peristaltic reflex in the isolated colon of the guinea‐pig or cat

“…In the colon the contraction above the bolus and the descending inhibition are suppressed by hexamethonium. Our results agree with most authors (Raiford & Mulinos, 1934;Schaumann, 1955;Kosterlitz & Robinson, 1957;Lee, 1960 ;Thouvenot & Harichaux, 1961 ;Kosterlitz, 1967;Hukuhara & Neya, 1968) in that atropine blocks the emptying phase of the peristaltic reflex not only in the ileum but also in the colon. However, when a solid bolus is the stimulus, it is found that, both in the guinea-pig and the cat, atropine is able to block propulsion by preventing selectively the relaxation below the bolus.…”

“…In our opinion the descending inhibition, which involves muscarinic receptors, is the basis for an explanation of the polarity of propulsion. This polarity has been claimed to be of myogenic or neurogenic nature (Raiford & Mulinos, 1934;Bozler, 1949a, b;Hukuhara, Yamagami & Nakayama, 1958;Nishio & Saito, 1965). Our experiments indicate that, in the presence of atropine, the distension of the balloon causes contractions above and below the bolus; we may therefore infer that the polarity is not inherent in the excitatory pathways.…”

An Investigation of the Peristaltic Reflex in Relation to Anatomical Observations

“…In the present investigation an attempt was made to determine the extent to which sensory impulses originating in the mucous membrane played a part. The response to tactile stimuli of the mucosa has been studied by Raiford and Mulinos [1934] who came to the conclusion that nervous connexions existed between the mucosa and the muscle coats, and that the contractions were due to a true local reflex which could be abolished by the application of cocaine to the mucosal surface. Gregory [1950] observed that the transport of fluid through extrinsically denervated loops of intestine was increased if the fluid was acid or hypertonic;…”

Muscarinic receptor 1 allosteric modulators stimulate colorectal emptying in dog, mouse and rat and resolve constipation

“…Early studies using non‐subtype selective antagonists demonstrated an essential role of acetylcholine (ACh), acting through muscarinic receptors, in the control of gastrointestinal movements in animal models and in human . More recently, subtypes of muscarinic receptors (M1r, M2r, and M3r) have been identified on enteric neurons and muscle in human, and in the small intestine and colon of experimental animals .…”