5-Hydroxytryptamine increases contractile force in porcine right atrium but not in left ventricle.
Positive chronotropic as well as inotropic effects of 5-hydroxytryptamine (5-HT) have been observed in pig atrial tissue, but no data are available about the direct effects of 5-HT on ventricular tissue. In the present study we investigated inotropic effects of 5-HT on atrial and ventricular trabeculae obtained from hearts of 3 months old pigs. The baseline isometric contractile force was significantly higher in ventricular (4.14 +/- 1.25 mN) than in atrial tissue (0.47 +/- 0.11 mN). A noradrenaline concentration-response curve (0.01 to 10 mumol/l) was used to check contractile responsiveness of the tissue and all responses were expressed as percentage of the response to 10 mumol/l noradrenaline. Noradrenaline caused a concentration-dependent increase in contractile force in both atrial and ventricular trabeculae. In contrast, though 5-HT (0.01 to 100 mumol/l) did increase force of contraction in atrial tissue (maximum: 72 +/- 20% of the response to noradrenaline 10 mumol/l), the contractility of ventricular trabeculae was not significantly affected (maximum: 12 +/- 6%). The present data show that, in contrast to atrial tissue, contractile force of ventricular tissue could not be significantly affected by 5-HT. To our knowledge, this is the first study to show that an agent which increased force of contraction in the atrium, did not have a corresponding effect on the ventricle. These findings may have important implications for a better understanding of the physiology and pharmacology of cardiac contractility.
Schoemaker
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RG
Department of Pharmacology, Faculty of Medicine and Health Sciences, Erasmus University Rotterdam, The Netherlands.
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D000818:Animals; D016280:Atrial Function, Right / Q000187:drug effects*; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013552:Swine; D000077526:Tropisetron; D016277:Ventricular Function, Left / Q000187:drug effects*
D007211:Indoles; D012702:Serotonin Antagonists; D012701:Serotonin; D000077526:Tropisetron