Effects of
nizofenone, an agent which has been known to have a protective effect against experimental
cerebral ischemia or
anoxia, on the action potential of guinea-pig papillary muscle and S-A node and dog Purkinje fibers were studied.
Nizofenone (10(-6) and 10(-5) M) significantly prolonged the action potential duration of guinea-pig papillary muscle and dog Purkinje fibers accompanying prolongation of the effective refractory period in dog Purkinje fibers.
Nizofenone decreased Vmax at the concentrations of 10(-5) and 10(-4) M in guinea-pig papillary muscle and
at 10(-4) M in dog Purkinje fibers.
Nizofenone suppressed the spontaneous activity of dog Purkinje fibers and guinea-pigs S-A node at the concentrations of 3 X 10(-5) to 10(-4) M and 10(-5) M, respectively.
Nizofenone (10(-4) M) decreased the contractile force of guinea-pig papillary muscle. In the guinea-pig papillary muscle, the effect of
nizofenone on action potential duration was almost the same as that of
quinidine, but the inhibitory effect on Vmax was slightly weaker than
quinidine. These results suggest that
nizofenone has a so-called "
quinidine-like action" on cardiac membrane.