Role of 5‐HT3 receptors in peristaltic reflex elicited by stroking the mucosa in the canine jejunum.

Abstract

SUMMARY1. The role played by the 5-HT3 receptor, a serotonin subtype receptor, in peristaltic reflexes was studied in dogs first given ketamine, then anaesthetized with urethane (10 g kg-', i.v.) and a-chloralose (100 mg kg-', i.v.). The jejunal loop was partitioned into two segments with respect to blood supply. Drugs were infused intra-arterially into each segment.2. Stroking of the mucosa of the aboral and oral segments elicited an ascending contraction and a descending relaxation, respectively.3. The ascending contraction was concentration-dependently inhibited by treatment of the aboral segment with the 5-HT3 receptor antagonists ICS 205-930 and ondansetron (1-4 pmol min-' to 14 nmol min-' for both). The maximal inhibition was 49*5 and 69-3 %, respectively. The response was not affected by treatment of the oral segment with these drugs. The descending relaxation was inhibited by 51-4 and 60-8 %, respectively, by treatment of the oral segment with ICS 205-930 and ondansetron (1-4 nmol min-' for both).4. The ascending contraction was markedly inhibited by treatment of either segment with hexamethonium (140 nmol min-'). The response was abolished by treating both segments with hexamethonium and by treating the oral segment with atropine (14 nmol min-').5. These results suggest firstly that, in the canine jejunum, enteric neurons with 5-HT3 receptors play a role as sensory neurons or interneurons in the ascending excitatory and the descending inhibitory pathways of the peristaltic reflex elicited by stroking the mucosa, and secondly, that the ascending limb is composed of cholinergic interneurons and motoneurons.

Effects of a 5‐HT3 antagonist, ondansetron, on fasting and postprandial small bowel water content assessed by magnetic resonance imaging

“…Mechanical stimulation of the mucosa is known to stimulate secretions via serotonin release 18 and to stimulate propulsive motility via 5-HT 3&4 receptor stimulation. 39 Nausea and stress induced by intubation also have a role in accelerating small bowel transit. 40,41 Stress from the intubation procedures or from disturbed sleep due to the presence of the tube might therefore have had an influence on the amount of SBWC.…”

5‐HT3 and 5‐HT4 receptor‐mediated facilitation of the emptying phase of the peristaltic reflex in the marmoset isolated ileum

“…In this respect, it has been shown that stimulation of the 5-HT4 receptor increases longitudinal muscle contraction (Buchheit & circular muscle contraction during peristalsis in the guinea-pig isolated ileum Costall et al, 1993). The 5-HT3 receptor has also been shown to increase the ascending excitatory effect but not the descending inhibitory effect in the guinea-pig isolated ileum (Yuan et al, 1994), whereas Neya et al (1993) report that 5-HT3 receptor stimulation enhances both the ascending excitatory and descending inhibitory effects in the infused canine jejunum. Whilst the presence of the 5-HT3 receptor antagonist, tropisetron or ondansetron does not affect the threshold for peristalsis in the guinea-pig isolated ileum Costall et al, 1993), this does not exclude a 5-HT3 receptor involvement in the peristaltic reflex since a higher concentration of 5-HT has been shown to reduce the threshold for peristalsis by stimulation of a 5-HT3 receptor (Tuladhar et al, 1995).…”

Expression and function of 5-HT3receptors in the enteric neurons of mice lacking the serotonin transporter

“…They rapidly depolarize neurons (20,47) by invoking a fast inward current (70,71), which is responsible for 5-HT-mediated fast neurotransmission (71). A combination of 5-HT 3 and 5-HT 4 antagonists inhibits the peristaltic reflex (39,51,52). 5-HT 3 antagonists decrease the frequency of migrating motor complexes in the isolated murine terminal ileum and colon (9).…”