Key result
Electrical reexcitation of rat papillary muscle at short intervals (50-80 ms) produced action potentials without significant mechanical response, which recovered at intervals >80 ms.
The study demonstrates that excitation-contraction coupling in rat papillary muscles passes through a refractory stage, likely due to the depletion of an intracellular releasable calcium fraction.
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Hypothesis-generating for calcium-dependent cardiac refractoriness; leaves open relevance to human electromechanical coupling or arrhythmias.
Mainwood et al. (1969) studied this question. Electrical reexcitation at short intervals (50 to 80 milliseconds) vs. Longer intervals (>80 milliseconds) was evaluated on Action potentials and mechanical response. Electrical reexcitation of rat papillary muscle at short intervals (50-80 ms) produced action potentials without significant mechanical response, which recovered at intervals >80 ms.
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