Peristaltic reflex

Bayliss and Starling [ 104] described the peristaltic reflex of small intestine in 1899. This enterically controlled reflex elicits a contraction oral to and a relaxation distal to a segmental distension, resulting in the movement of contents in the aboral direction [104], The peristaltic reflex is funda-... 

Spencer NJ, Smith TK Simultaneous intracellular recordings from longitudinal and circular muscle during the peristaltic reflex in guinea-pig distal colon. J Physiol 2001 533 ... 

In the periphery, 5-HT4 receptor mRNA is found in vascular smooth muscle. Newly developed drugs that activate 5-HT4 receptors are of interest for their potential in treating cardiac arrhythmia. The 5-HT4 receptor is also located on neurons of the alimentary tract, for example the myenteric plexus of the ileum, and on smooth muscle cells and secretory cells of the gastrointestinal tract, where they evoke secretions and the peristaltic reflex. 5-HT4 receptor agonists (e.g. cisapride, prucalopride, tegaserod) are used therapeutically in the treatment of constipation-predominant irritable bowel syndrome and in functional motility disorders of the upper gastrointestinal tract. 

Schneider et al. (S6, S7, S8) have demonstrated that wheat gluten and certain gluten fractions cause inhibition of the isolated small intestine of the rat. In the Trendelenburg preparation, as modified by Biilbring et al. (B21), inhibition of the peristaltic reflex occurred if the material was placed outside the intestine so that it could reach the muscle without traversing the mucous membrane. If it was placed inside the lumen no inhibitory effect was seen. If the gluten or gluten fractions were incubated with rat mucous membrane extract, complete inactivation of the inhibitory effect was obtained. This action of mucous... 

Inhibitory effect on peristaltic reflex in isolated rat intestine + + + — + —... 

Schneider, R., Bishop, H., and Shaw, B., The inhibition of die peristaltic reflex by substances from protein sources. Brit. J. Pharmacol. 15, 219-223 (1960). 

Mechanism of Action An anti-irritable bowel syndrome (IBS) agent that binds to 5-HT receptors in the GI tract. Therapeutic Effect Triggers a peristaltic reflex in the gut, increasing bowel motility. 

Stimulation of 5-HT4 receptors on the presynaptic terminal of submucosal intrinsic primary afferent nerves enhances the release of their neurotransmitters, including calcitoningene-related peptide, which stimulate second-order enteric neurons to promote the peristaltic reflex (Figure 62-4). These enteric neurons stimulate proximal bowel contraction (via acetylcholine and substance P) and distal bowel relaxation (via nitric oxide and vasoactive intestinal peptide). 

Storr M, Hahn A, Gaffal E et al (2002) Effects of endomorphin-1 and -2 on on mu-opioid receptors in myenteric neurons and in the peristaltic reflex in rat small intestine. Clin Exp Pharmacol Physiol 29 428-34... 

Paton and Zar (1968) described the dissection of the MP-LMP of the guinea-pig small intestine. This preparation has been invaluable in the study of neurotransmission from the myenteric plexus to the longitudinal smooth muscle, particularly by opioids and cannabinoids, without the confounding effects of the peristaltic reflex. A similar preparation has been used to study neuromuscular transmission to the circular smooth muscle (Izzo et al. 1998). Contractions of MP-LMP induced by electrical field stimulation (EES) were potently inhibited in a concentration-dependent fashion by the cannabinoid receptor agonists CP 55,940, CP 50,556, WIN 55,212-2, nabilone, CP 56,667, A -THC and cannabinol (Coutts and Pertwee 1997 Pertwee 2001). This inhibition was competitively and reversibly antagonised by SR141716A, without any effect on the inhibitory responses to normorphine... 

Tegaserod maleate is a GI agent that binds with high affinity to human 5-HT4 receptors, acting as an agonist at neuronal 5-HT4 receptors to trigger the release of neurotransmitters. Activation of 5-HT4 receptors in the GI tract stimulates peristaltic reflex and intestinal secretion, and inhibits visceral sensitivity. It is used for short-term treatment of women with irritable bowel syndrome (IBS) whose primary symptom is constipation and in treatment of patients younger than 65 years of age with chronic idiopathic constipation. 

HT RECEPTORS 5-HT receptors are widely distributed throughout the body. In the CNS, the receptors are found on neurons of the superior and inferior colliculi and in the hippocampus. In the GI tract, 5-HT receptors are located on neurons of the myenteric plexus and on smooth muscle and secretory cells. The 5-HT receptor is thought to evoke secretion in the alimentary tract and to facilitate the peristaltic reflex. 5-HT receptors couple to G to activate adeny-lyl cyclase, leading to a rise in intracellular levels of cyclic AMP, possibly accounting for the utility of prokinetic benzamides in GI disorders (see Chapter 37). 

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