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Effect of urapidil on the action potentials in the guinea-pig ventricular myocardium

✍ Scribed by Noriyasu Noguchi; Junichi Hasegawa; Hiroki Omodani; Takahiro Nawada; Satoshi Matsuoka; Ichiro Hisatome; Hiroshi Kotake; Hiroto Mashiba

Publisher
Springer US
Year
1991
Tongue
English
Weight
343 KB
Volume
5
Category
Article
ISSN
0920-3206

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✦ Synopsis

The electrophysiological effects of urapidil, a new aradrenoceptor antagonist, were assessed in the reserpinized guinea-pig ventricular myocardium. Urapidil suppressed the maximal rate of rise (Vm~) of steady-state action potentials elicited by the fast responses at high concentrations independently of blockade of myocardial a-adrenoceptors, but not the ~'m~x of CaZ+-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 resuits suggest that the inhibitory effect of urapidil on the slow inward Ca 2+ current and the Na + current is in practice negligible.

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