Electrophysiological effects of platelet-activating factor (PAF-acether) in guinea-pig papillary muscles.
The effects of PAF-acether (10(-11) to 10(-7) M) were studied on the electrical and mechanical activity of guinea-pig papillary muscles. At 10(-11) M PAF-acether did not modify the amplitude and Vmax of the upstroke or the resting membrane potential. At higher concentrations PAF-acether produced a dose-dependent increase in the amplitude and Vmax of the upstroke, shortened the action potential duration and hyperpolarized the resting membrane potential. These effects were accompanied by a biphasic effect on ventricular contractile force. The shortening of the APD was inhibited in muscles pretreated with tetraethylammonium or verapamil. In papillary muscles depolarized by 27 mM K Tyrode solution PAF-acether induced slow action potentials which were blocked by verapamil. PAF-acether produced a dose-dependent increase in amplitude and Vmax of the upstroke on the slow action potentials elicited by isoproterenol, prolonged the action potential duration and hyperpolarized the resting membrane potential. These results suggest that in guinea-pig papillary muscles PAF-acether increased Ca influx via the slow inward current.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects* / Q000502:physiology; D010972:Platelet Activating Factor; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D010972:Platelet Activating Factor; D013757:Tetraethylammonium Compounds; D014700:Verapamil; D002118:Calcium