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 (V(max)) 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 (10-7M 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 10-6M, it increased both RP and the amplitude of AP and caused a dose-dependent shortening of the repolarization. Neither PAF (10 -11 to 10-7M) nor BN 52021 (10-5 M) was able to induce slow AP in guinea-pig atrial and ventricular preparations depolarized by 25mM 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.
|Number of pages||8|
|Journal||Drugs under Experimental and Clinical Research|
|Publication status||Published - Jan 1 1992|
ASJC Scopus subject areas
- Molecular Medicine
- Drug Discovery
- Pharmacology (medical)