Nicorandil shortens action potential duration and antagonises the reduction of V max by lidocaine but not by disopyramide in guinea-pig papillary muscles

1988 ◽  
Vol 337 (2) ◽  
Author(s):  
Michio Kojima ◽  
Takashi Ban
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Action Potential Duration ◽  
Papillary Muscles

Dual effects of external magnesium on action potential duration in guinea pig ventricular myocytes

1995 ◽  
Vol 268 (6) ◽  
pp. H2321-H2328 ◽  
Author(s):  
S. Zhang ◽  
T. Sawanobori ◽  
H. Adaniya ◽  
Y. Hirano ◽  
M. Hiraoka
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Decay Time ◽  
Action Potential Duration ◽  
Time Course ◽  
Ventricular Myocytes ◽  
Membrane Surface ◽  
Surface Charges ◽  
Whole Cell Patch Clamp ◽  
K Current

Effects of extracellular magnesium (Mg2+) on action potential duration (APD) and underlying membrane currents in guinea pig ventricular myocytes were studied by using the whole cell patch-clamp method. Increasing external Mg2+ concentration [Mg2+]o) from 0.5 to 3 mM produced a prolongation of APD at 90% repolarization (APD90), whereas 5 and 10 mM Mg2+ shortened it. [Mg2+]o, at 3 mM or higher, suppressed the delayed outward K+ current and the inward rectifier K+ current. Increases in [Mg2+]o depressed the peak amplitude and delayed the decay time course of the Ca2+ current (ICa), the latter effect is probably due to the decrease in Ca(2+)-induced inactivation. Thus 3 mM Mg2+ suppressed the peak ICa but increased the late ICa amplitude at the end of a 200-ms depolarization pulse, whereas 10 mM Mg2+ suppressed both components. Application of 10 mM Mg2+ shifted the voltage-dependent activation and inactivation by approximately 10 mV to more positive voltage due to screening the membrane surface charges. Application of manganese (1-5 mM) also caused dual effects on APD90, similar to those of Mg2+, and suppressed the peak ICa with slowed decay. These results suggest that the dual effects of Mg2+ on APD in guinea pig ventricular myocytes can be, at least in part, explained by its action on ICa with slowed decay time course in addition to suppressive effects on K+ currents.

Action potential duration and force-frequency relationship in isolated rabbit, guinea pig and rat cardiac muscle

1996 ◽  
Vol 166 (2) ◽  
pp. 150-155 ◽  
Author(s):  
P. Szigligeti ◽  
C. Pankucsi ◽  
T. B�ny�sz ◽  
A. Varr� ◽  
P. P. N�n�si
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Cardiac Muscle ◽  
Action Potential Duration ◽  
Force Frequency ◽  
Frequency Relationship
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