Electrophysiological effects of EGIS-7229, a new antiarrhythmic agent, in isolated guinea pig papillary muscle.
1. The cellular electrphysiological effects of EGIS-7229, a novel antiarrhythmic agent, were studied in guinea pig papillary muscles with the use of conventional microelectrode techniques. 2. The drug had a concentration-dependent biphasic effect on action potential duration (APD). APD was significantly lengthened at low concentration (3 mumol/1), whereas it was shortened at concentrations higher than 10 mumol/l. 3. At concentrations higher than 10 mumol/l, the drug decreased the maximum velocity of action potential upstroke (Vmax), the force contraction, and altered the restitution kinetics of APD. 4. The effect of EGIS-7229 on Vmax was frequently dependent; it was most prominent at short pacing cycle lengths (use-dependent block). 5. On the basis of present results, EGIS-7229 appears to carry mixed class I and class III characteristics. Class III properties are present at low concentrations, whereas, at higher concentrations, class I actions may be predominant.
Pankucsi
C
C
Department of Physiology, University Medical School of Debrecen, Hungary.
Bányász
T
T
Magyar
J
J
Gyönös
I
I
Kovács
A
A
Szénási
G
G
Varró
A
A
Nánási
P P
PP
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D010210:Papillary Muscles / Q000187:drug effects* / Q000502:physiology; D011724:Pyridazines / Q000494:pharmacology*
D000889:Anti-Arrhythmia Agents; C106729:EGIS 7229; D011724:Pyridazines