Key result
Although 4-AP-sensitive transient outward current increases postnatally, its time course differs from action potential shortening, suggesting it is not responsible for most postnatal APD shortening.
Population
Rat ventricular isolated cells and papillary muscles at postnatal day 1, days 8-10, and adult stages
Comparison
2 mM 4-aminopyridine (4-AP) vs Baseline and comparison across developmental…
Design
Preclinical
Authors
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Ito unlikely primary driver of postnatal APD shortening in rats; leaves open dominant mechanisms and translational relevance.
The different time courses of action potential shortening and increases in transient outward current suggest that Ito is unlikely to be the primary driver of postnatal action potential shortening in rat ventricular cells.
Wahler et al. (1994) studied this question. 4-aminopyridine (4-AP) was evaluated on Action potential duration at 25% repolarization (APD25) and transient outward current (Ito). Although 4-AP-sensitive transient outward current increases postnatally, its time course differs from action potential shortening, suggesting it is not responsible for most postnatal APD shortening.
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