Effects of @entity5834 , XXXX , and @entity8452 on @entity460 -dependent oscillations in @entity742 cardiac Purkinje fibers.

@entity742 @entity141 @entity8452 @entity5834 @entity6513 @entity460 @entity2701
Membrane current and @entity2701 were measured in voltage-clamped @entity742 cardiac Purkinje fibers. Elevating the intracellular @entity460 concentration ([ @entity141 ]i) results in oscillations of membrane current and @entity2701 both at rest and during stimulation. During stimulation, an oscillatory transient inward current and an after contraction follow repolarization. We have examined the effects on the oscillations of changing the extracellular @entity460 concentration ([ @entity141 ]o) and of adding various drugs. In agreement with previous work, high concentrations of drugs that affect the sarcoplasmic reticulum, namely @entity5834 (10-20 mM), @entity6513 (1 mM), and @entity8452 (10 microM), abolish the oscillations. However, at lower concentrations, these three drugs have different effects on the oscillations. @entity5834 (1-2 mM) decreases the oscillation amplitude but increases the frequency. @entity6513 (100-500 microM) has little effect on the magnitude of the oscillations but decreases their frequency. @entity8452 , at all concentrations used (0.1-10 microM), eventually abolishes the oscillations but, in doing so, decreases the magnitude, leaving the frequency unaffected. When [ @entity141 ]o was changed in order to vary [ @entity141 ]i, both the frequency and the magnitude of the oscillations always changed in the same direction. This suggests that these three drugs have effects in addition to just changing [ @entity141 ]i.
