ISSN:
1435-1803
Keywords:
sheep cardiacPurkinje fibres
;
voltage clamped fibres
;
tetrodotoxin
;
lidocaine
;
quinidine
;
transient inward current
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effect of tetrodotoxin (TTX), lidocaine, and quinidine on the transient inward current (TI) was studied in voltage-clamped sheep cardiac Purkinje fibres. The TI was induced by elevation of extracellular Ca or addition of strophanthidin. Reduction of external Na had a biphasic effect on the steady state TI magnitude; a moderate (〈50%) reduction of external Na had an enhancing effect on the TI; a further decrease of extracellular Na was accompanied by a decline of TI amplitude. The TI could not be induced in Na-free medium (external Ca≦9.0 mM). TTX, lidocainc, and quinidine reduced the magnitude of the TI in a dose-dependent way. The blocking effect of these agents could be compensated for by a moderate (〈50%) reduction of external Na or an elevation of extracellular Ca. It is suggested that the blocking effect of TTX, lidocaine, and quinidine on the TI is due to a reduction of intracellular Na, which causes a decay of intracellular Ca via the Na−Ca exchange mechanism.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01907272
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