title: Cellular electrophysiological effects of platelet-activating factor (PAF) and its antagonist BN 52021 in cardiac preparations.
abstract: The effects of PAF and its antagonist BN 52021 were studied on the transmembrane action potential (AP) in atrial and ventricular papillary muscles of guinea-pig. PAF (10(-11)-10(-7) M) did not modify the resting membrane potential (RP) nor the maximum rate of depolarization (Vmax) either in atrial or in ventricular fibres. At 10(-11) M, PAF increased the amplitude of AP both in atrial and ventricular muscles. the repolarization phase was dose-dependently shortened in the case of atrium, while the duration of ventricular AP was somewhat increased. The K+ channel blocker 4-aminopyridine (10(-3) M) prevented the effect of PAF on the duration of atrial AP. BN 52021 (10(-7) M to 10(-5) M) produced a significant shortening of the duration of atrial AP and did not modify the other parameters. In papillary muscle up to 10(-6) M, it increased both RP and the amplitude of AP and caused a dose-dependent shortening of the repolarization. Neither PAF (10(-11) to 10(-7) M) nor BN 52021 (10(-5) M) was able to induce slow AP in guinea-pig atrial and ventricular preparations depolarized by 25 mM K+ Tyrode solution. PAF did not modify the slow AP elicited by isoprenaline (5 x 10(-7) M). The present findings suggest that neither PAF nor BN 52021 affects slow inward Ca2+ current but their effects on other ionic currents, e.g. K+ currents, may be important.
authors.affiliation: Department of Pharmacology, Semmelweis University of Medicine, Budapest, Hungary.
authors.forename: V
authors.initials: V
authors.lastname: Kecskemeti
authors.forename: P
authors.initials: P
authors.lastname: Braquet
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004224:Diterpenes; D004305:Dose-Response Relationship, Drug; D046934:Ginkgolides; D006168:Guinea Pigs; D007783:Lactones / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology*; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects
chemical_list: D004224:Diterpenes; D046934:Ginkgolides; D007783:Lactones; D010972:Platelet Activating Factor; D015221:Potassium Channels; D015761:4-Aminopyridine; C045856:ginkgolide B; D002118:Calcium