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5-Hydroxytryptamine stimulates human isolated atrium but not ventricle
R G Schoemaker1, X Y Du, W A Bax
1Department of Pharmacology, Faculty of Medicine and Health Sciences, Erasmus University Rotterdam, Netherlands.
European Journal of Pharmacology
|January 5, 1993
Summary
5-hydroxytryptamine (5-HT) positively impacts atrial contraction but not ventricular contraction in humans. This suggests 5-HT4 receptor agonists may be safe for gastrointestinal treatments without causing heart side effects.
Area of Science:
- Cardiology
- Pharmacology
- Physiology
Background:
- 5-hydroxytryptamine (5-HT) is known to have positive inotropic effects on the human atrium via 5-HT4 receptors.
- Limited data exists regarding 5-HT's effects on the ventricular myocardium.
Purpose of the Study:
- To investigate the inotropic effects of 5-HT on human ventricular trabeculae.
- To compare these effects with those observed in human right atrial trabeculae.
Main Methods:
- Human ventricular and atrial trabeculae were isolated.
- Baseline contractile force and response to noradrenaline were measured.
- The effects of 5-HT on contractile force were assessed.
Main Results:
- Ventricular trabeculae exhibited significantly higher baseline force of contraction and noradrenaline response compared to atrial trabeculae.
- 5-HT (at 10(-4) M) increased atrial trabeculae contraction but had no effect on ventricular trabeculae contraction.
Conclusions:
- 5-HT is ineffective as a positive inotropic agent in human ventricular trabeculae, unlike in atrial tissue.
- This ineffectiveness suggests that 5-HT4 receptor agonists could be safely developed for gastrointestinal disorders without causing ventricular side effects.