Summary
The electrophysiological effects of urapidil, a new α1-adrenoceptor antagonist, were assessed in the reserpinized guinea-pig ventricular myocardium. Urapidil suppressed the maximal rate of rise (αmax) of steady-state action potentials elicited by the fast responses at high concentrations independently of blockade of myocardial α-adrenoceptors, but not the αmax of Ca2+-dependent slow action potentials of partially depolarized muscles in concentrations tested (up to 1.1 mM). Urapidil at high concentrations prolonged the action potential durations of the fast and slow responses in a manner similar to the quinidine-like antiarrhythmic drugs. These results suggest that the inhibitory effect of urapidil on the slow inward Ca2+ current and the Na+ current is in practice negligible.
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Noguchi, N., Hasegawa, J., Omodani, H. et al. Effect of urapidil on the action potentials in the guinea-pig ventricular myocardium. Cardiovasc Drug Ther 5, 987–990 (1991). https://doi.org/10.1007/BF00143525
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DOI: https://doi.org/10.1007/BF00143525