Cardiac electrophysiological effects of a new dihydropyridine calcium antagonist (BBR 2160)

BBR 2160 is a new dihydropyridine derivative belonging to the group of the so-called tiampidines. We used intracellular microelectrodes to characterize the electrophysiological properties of BBR 2160 on sheep Purkinje fibres and guinea-pig papillary muscle. BBR 2160 (10(-7) and 10(-6) M) dose dependently decreased the contractility of driven Purkinje fibre and papillary muscle. This effect was associated with a lowering of the plateau phase and a shortening of action potential duration in papillary muscle. The effect of the drug developed quite slowly over time. The amplitude and Vmax of normal action potential were not affected by BBR 2160. Instead BBR 2160 reduced the amplitude and Vmax of the slow action potentials (which are a relatively good index of the slow inward current) induced by histamine (10(-5) M) in K(+)-depolarized (22 mM) papillary muscle. The results suggest that BBR 2160 has calcium-antagonistic properties in cardiac tissue.