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Strontium, nifedipine and 4‐aminopyridine modify the time course of the action potential in cells from rat ventricular muscle
Author(s) -
Mitchell Mary R.,
Powell T.,
Terrar D. A.,
Twist V.W.
Publication year - 1984
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1984.tb10108.x
Subject(s) - nifedipine , depolarization , strontium , cardiac transient outward potassium current , 4 aminopyridine , calcium , repolarization , chemistry , cardiac action potential , electrophysiology , biophysics , myocyte , medicine , endocrinology , biology , patch clamp , potassium channel , organic chemistry
1 Action potentials, initiated by brief depolarizing pulses, were recorded from single cells isolated from rat ventricular muscle. These action potentials showed a rapid upstroke to about + 30 mV, followed by two phases of repolarization referred to as the early and late phases of the action potential. 2 Nifedipine (1 μ m ), which blocks the second inward current (I si ) carried by Ca in these cells, shortened the early phase. 3 Substitution of strontium for calcium in the solution bathing the cells, a procedure which prolongs I si , prolonged the early phase. 4 4‐Aminopyridine (1 m m ), which inhibits transient outward current, prolonged the early phase with either calcium or strontium in the external solution. 5 It is concluded that both I si and transient outward current contribute to the early phase of the action potential in rat ventricular muscle. It is also suggested that I si does not directly contribute to the late phase, since the characteristics of the late phase are not compatible with such a role, and the possibility of additional inward current is investigated in the accompanying paper (Mitchell et al. , 1984).