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  • Title: Cellular electrophysiological effects of platelet-activating factor (PAF) and its antagonist BN 52021 in cardiac preparations.
    Author: Kecskemeti V, Braquet P.
    Journal: Drugs Exp Clin Res; 1992; 18(1):9-16. PubMed ID: 1600866.
    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.
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