Effect of antiarrhythmic drugs, TTX, and 4-aminopyridine on repetitive electrical activity in frog skeletal muscle.
1. Conventional microelectrode techniques were used to study the effects of antiarrhythmic drugs (quinidine, 2-20 microM; lidocaine, 5-50 microM; verapamil, 2-20 microM), 4-aminopyridine (4-AP, 50-100 microM), and tetrodotoxin (TTX, 1.5-6 nM) on repetitive electrical discharges induced in the muscle membrane in the presence of 1 microM cevadine. 2. Antiarrhythmic drugs and 4-AP produced progressive reduction of the maximum upstroke velocity (V+ max) of the discharges, while the cycle length was prolonged by each drug except 4-AP. 3. The efficacy in depression of V+ max and prolongation of cycle length was not proportional in the case of individual drugs. 4. A simple model of the repetitive activity incorporating drug-effects was presented. The cevadine-modified Na+ channels could be blocked by antiarrhythmic agents, however, the efficacy of these drugs on the normal and cevadine-modified Na+ channels were found to be different.
Nánási
P P
PP
Department of Physiology, University Medical School of Debrecen, Hungary.
Dankó
M
M
Lathrop
D A
DA
D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D004594:Electrophysiology; D066298:In Vitro Techniques; D007700:Kinetics; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D011893:Rana esculenta; D015222:Sodium Channels / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology*; D014702:Veratrine / Q000494:pharmacology
D000889:Anti-Arrhythmia Agents; D015222:Sodium Channels; D013779:Tetrodotoxin; D015761:4-Aminopyridine; D014702:Veratrine