5-HT3 receptor involvement in descending reflex relaxation in the rabbit isolated distal colon

Eliana Messori, Stefano M. Candura, Teresa Coccini, Barbara Balestra, Marcello Tonini

Research output: Contribution to journalArticlepeer-review


In whole segments of rabbit distal colon with mucosa removed, descending reflex relaxations of the circular muscle (descending inhibition) elicited by inflating (0.1-1 ml) an intraluminal balloon, were partially antagonized by 100 μM hexamethonium and the 5-HT3 receptor antagonist, ondansetron (3 μM), and abolished by 1 μM tetrodotoxin. The inhibitory effects of hexamethonium and ondansetron were additive. Conversely, hexamethonium (100 μM) and ondansetron (3 μM) failed to reduce electrically induced non-adrenergic non-cholinergic (NANC) relaxations of colonic circular muscle. It is concluded that interneuronally released acetylcholine and 5-hydroxytryptamine (5-HT) activate descending inhibitory pathways supplying the circular coat, via nicotinic and 5-HT3 receptors, respectively. This evidence suggests a functional involvement of 5-hydroxytryptaminergic transmission in the descending inhibition of rabbit colon.

Original languageEnglish
Pages (from-to)205-208
Number of pages4
JournalEuropean Journal of Pharmacology
Issue number2
Publication statusPublished - Nov 14 1995


  • 5-HT (5-hydroxytryptamine, serotonin)
  • 5-HT receptor antagonism
  • Descending inhibition
  • Neuro-neuronal transmission

ASJC Scopus subject areas

  • Pharmacology
  • Cellular and Molecular Neuroscience


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