Key result
Repetitive stimulation at 2-4 Hz in guinea-pig papillary muscle increased intracellular sodium and extracellular potassium, while post-stimulation hyperpolarization was largely explained by extracellular potassium depletion.
Why the study?
Does repetitive stimulation alter intra- and extracellular potassium and intracellular sodium activities and membrane potential in guinea-pig papillary muscle?
Does repetitive stimulation alter intra- and extracellular potassium and intracellular sodium activities and membrane potential in guinea-pig papillary muscle?
In guinea-pig papillary muscle, hyperpolarization following repetitive stimulation is primarily driven by extracellular potassium depletion due to Na-K pump activity rather than an electrogenic component.
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Animal data on stimulation-induced ion shifts warrant caution in extrapolating to patients; leaves open mechanisms of post-pacing hyperpolarization in human myocardium.
Hotokebuchi et al. (1987) studied Normal cardiac electrophysiology (guinea-pig papillary muscle). Repetitive electrical stimulation vs. Low frequency stimulation (0.1-0.2 Hz) was evaluated on Changes in membrane potential and intracellular sodium/potassium activities. Repetitive stimulation at 2-4 Hz in guinea-pig papillary muscle increased intracellular sodium and extracellular potassium, while post-stimulation hyperpolarization was largely explained by extracellular potassium depletion.
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