Key result
Tetrodotoxin (10-20 microM) completely blocked Na+ channels when applied to the outside membrane surface of neonatal rat cardiac cells, but had no effect when applied from the inside.
Population
Primary cardiac cell cultures prepared from the hearts of neonatal rats
Comparison
Patch-clamp method and tetrodotoxin application vs Cell-attached patches versus inside-out patches
Design
Preclinical
Authors
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Confirms extracellular TTX blockade of Na+ channels in neonatal rat cardiomyocytes; leaves open sidedness and relevance in adult human myocardium.
This preclinical study characterizes the electrophysiological properties of sodium channels in neonatal rat cardiac cells, demonstrating differences in kinetics between cell-attached and inside-out patches and confirming extracellular blockade by tetrodotoxin.
Cachelin et al. (1983) studied this question. Tetrodotoxin was evaluated on Whole-cell and single-channel Na+ currents. Tetrodotoxin (10-20 microM) completely blocked Na+ channels when applied to the outside membrane surface of neonatal rat cardiac cells, but had no effect when applied from the inside.
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