5-Hydroxytryptamine stimulates net Ca2+ flux in the ventricular muscle of a mollusc (Busycon canaliculatum) during cardioexcitation.
Noninvasive, self-referencing calcium (Ca2+) electrodes were used to study the mechanisms by which 5-hydroxytryptamine (5-HT) affects net Ca2+ flux across the sarcolemma of myocytes from ventricular trabeculae (from a marine gastropod, Busycon canaliculatum). Treatment of isolated trabeculae with 5-HT causes a net Ca2+ efflux, which is 30% blocked by verapamil. These findings suggest that the efflux is in part the result of a previous Ca2+ influx through L-type Ca2+ channels and is due to a rapid Ca2+ extrusion mechanism inherent to the sarcolemma of these myocytes. 5-HT-induced net Ca2+ efflux is also reduced by about 40% by treatment with a sodium (Na+)-free, lithium (Li+)-substituted saline, which shuts down the Na-Ca exchanger during Ca2+ extrusion. Cyclopiazonic acid (CPA), an inhibitor of the sarcoplasmic reticulum (SR) Ca2+ ATPase, almost completely abolishes the 5-HT-induced net Ca2+ efflux, suggesting that the SR rather than the extracellular pool is the primary Ca2+ reservoir serving 5-HT-induced excitation.
Devlin
C L
CL
Department of Biology, Penn State University, Abington College, Pennsylvania 19001, USA. cld5@psu.edu
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008974:Mollusca / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D016276:Ventricular Function; D014700:Verapamil / Q000494:pharmacology*
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D007211:Indoles; D007476:Ionophores; D012701:Serotonin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D014700:Verapamil; D002118:Calcium; C000543:cyclopiazonic acid