Effect of putative carcinoid mediators on gastric and small bowel transit in rats and the role of 5‐HT receptors


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11 Scopus citations


Whereas serotonin and substance P stimulate in‐vivo and in‐vitro myoelectric activity in the small intestine, their effects on transit are unclear. We used a validated in‐vivo transit model in the chloral hydrate‐anaesthetized rat to study the effects of serotonin, substance P and motilin, three putative mediators of carcinoid diarrhoea, on transit through the upper digestive tract. Intra‐arterial serotonin accelerated gastric emptying of a radiolabeled liquid, while motilin accelerated overall upper gastrointestinal transit. Substance P slowed overall upper gastrointestinal transit without altering gastric emptying. The antagonists to serotonin receptor subtypes, R‐zacopride (5‐HT3) and ketanserin (5‐HT2), also accelerated rat gastric emptying of liquids; in contrast, a 5‐HT4 agonist, SC53116, resulted in a less pronounced effect on gastric emptying at the dose tested. We conclude that circulating substance P is unlikely to be an important accelerator of transit through the upper digestive tract; in contrast, hyperserotoninaemia significantly accelerates transit through the stomach, and 5‐HT2 and 5‐HT3 receptor subtypes may play a role in the motor effects of serotonin in the stomach.

Original languageEnglish (US)
Pages (from-to)61-66
Number of pages6
JournalAlimentary pharmacology & therapeutics
Issue number1
StatePublished - Feb 1993

ASJC Scopus subject areas

  • Hepatology
  • Gastroenterology
  • Pharmacology (medical)


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