title: Contractile effects of 5-hydroxytryptamine and 5-carboxamidotryptamine in the equine jejunum.
abstract: The use of human prokinetic drugs in colic horses leads to inconsistent results. This might be related to differences in gastrointestinal receptor populations. The motor effects of 5-hydroxytryptamine (5-HT; serotonin) on the equine mid-jejunum were therefore studied. Longitudinal muscle preparations were set up for isotonic measurement. 5-HT induced tonic contractions with superimposed phasic activity; these responses were not influenced by tetrodotoxin and atropine, suggesting a non-neurogenic, non-cholinergic pathway. The 5-HT receptor antagonists GR 127935 (5-HT(1B,D)), ketanserin (5-HT(2A)), SB 204741 (5-HT(2B)), RS 102221 (5-HT(2C)), granisetron (5-HT(3)), GR 113808 (5-HT(4)) and SB 269970 (5-HT(7)) had no influence on the 5-HT-induced response; the 5-HT(1A) receptor antagonists NAN 190 (pK(b)=8.13+/-0.06) and WAY 100635 (pK(b)=8.69+/-0.07), and the 5-HT(1,2,5,6,7) receptor antagonist methysergide concentration-dependently inhibited the 5-HT-induced contractile response. The 5-HT(1,7) receptor agonist 5-carboxamidotryptamine (5-CT) induced a contractile response similar to that of 5-HT; its effect was not influenced by tetrodotoxin and atropine, and SB 269970, but antagonised by WAY 100635. 8-OHDPAT, buspiron and flesinoxan, which are active at rat and human 5-HT(1A) receptors, had no contractile influence. These results suggest that the contractile effect of 5-HT in equine jejunal longitudinal muscle is due to interaction with muscular 5-HT receptors, which cannot be characterised between the actually known classes of 5-HT receptors.
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium. Catherine.Delesalle@UGent.be
authors.forename: Cathérine
authors.initials: C
authors.lastname: Delesalle
authors.forename: Piet
authors.initials: P
authors.lastname: Deprez
authors.forename: Jan A J
authors.initials: JA
authors.lastname: Schuurkes
authors.forename: Romain A
authors.initials: RA
authors.lastname: Lefebvre
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D006736:Horses; D007583:Jejunum / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects*; D012701:Serotonin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D018490:Serotonin Agents / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
chemical_list: D018490:Serotonin Agents; D017366:Serotonin Receptor Agonists; D012701:Serotonin; C047087:5-carboxamidotryptamine