5-HT3 receptors augment neuronal, cholinergic contractions in guinea pig trachea.
Serotonin (5-HT) and the selective 5-HT3 receptor agonist, 2-methyl-5-hydroxytryptamine enhanced electrical field stimulated contractions of the isolated guinea pig trachea. 5-HT (EC50 = 3.5 microM) was twice as potent as 2-methyl-5-hydroxytryptamine (EC50 = 7.4 microM). The effects of 5-HT and 2-methyl-5-hydroxytryptamine were antagonized by the selective 5-HT3 receptor antagonist; zacopride (apparent pA2 = 7.60 against 2-methyl-5-hydroxytryptamine). 2-Methyl-5-hydroxytryptamine (10 microM) had no effect on contractile responses to exogenous acetylcholine. Furthermore, the increase in electrical field stimulated contraction by 2-methyl-5-hydroxytryptamine was unchanged by hexamethonium (100 microM) but contractions were blocked by atropine (1 microM). These results suggest that excitatory 5-HT3 receptors exist on postganglionic cholinergic nerves in the isolated guinea pig trachea.
Rizzo
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CA
Schering-Plough Research Institute, Kenilworth, NJ 07033-0539.
Kreutner
W
W
Chapman
R W
RW
D000818:Animals; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects* / Q000294:innervation
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists