Dissociation of 5-hydroxytryptamine effects on myocardial contractility and cyclic AMP accumulation.
1 5-Hydroxytryptamine increased the contractility of the isolated rat atrium and produced a small rise in cyclic 3',5'-adenosine monophosphate (cyclic AMP) accumulation in rat heart slices. These effects were similar to those of tyramine.2 Incubation with phenoxybenzamine prevented the inotropic effect of 5-hydroxytryptamine but did not inhibit the rise in cyclic AMP accumulation.3 A single injection of reserpine 24 h before the experiment did not inhibit the inotropic effect of 5-hydroxytryptamine but prevented the rise in cyclic AMP accumulation.4 It is concluded that in the rat 5-hydroxytryptamine increases cardiac contractility chiefly by a direct effect which is blocked by phenoxybenzamine, whereas it increases myocardial cyclic AMP accumulation indirectly by releasing endogenous catecholamines. Cardiac contractility may thus be increased without a rise in cyclic AMP accumulation, and cyclic AMP accumulation may be increased without a rise in contractility.
D000225:Adenine / Q000378:metabolism; D000818:Animals; D002250:Carbon Radioisotopes; D003042:Cocaine / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004087:Dihydroergotamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000378:metabolism; D006892:Hydroxydopamines / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D013268:Stimulation, Chemical; D014316:Tritium; D014439:Tyramine / Q000494:pharmacology
D002250:Carbon Radioisotopes; D006892:Hydroxydopamines; D011506:Proteins; D010643:Phenoxybenzamine; D014316:Tritium; D012701:Serotonin; D004087:Dihydroergotamine; D009020:Morphine; D012110:Reserpine; D000242:Cyclic AMP; D003042:Cocaine; D000225:Adenine; D009638:Norepinephrine; D014439:Tyramine