At more positive potentials, adult, but not neonatal cells, displayed a transient outward current I to consistent with the presence of phase 1 repolarization in adult but not neonatal cells. Comparison of potassium currents in rabbit atrial and ventricular cells. Peak I Ca was found to be significantly smaller in neonate ventricular cells compared to adult cells Figure 9C. Age-related appearance of outward currents may contribute to developmental differences in ventricular repolarization. The composition of the Tyrode’s solution was in mM: E was a generous gift from Eisai Co.

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Figure 6A shows voltage clamp recordings of I Kr tail currents recorded from 2 week old neonate. In the adult mammalian heart, marked differences in the shape and duration of the cardiac action potential have been well described in different regions of ventricle [ 3 – 5 ]. Table 1 summarizes the effects of chromanol B and sotalol on APD 90 and development of early afterdepolarizations EADs in day old neonatal tissue.

Comparison of potassium currents in rabbit atrial and ventricular cells. Cardiac pacemaking in the sinoatrial node.

Recordings were started 30 min after the addition of d-sotalol or chromanol B. Hope that helps in figuring out an answer. We next determined the ionic basis for action potential distinctions between cells isolated from adult and 2 week old dogs.


Several functions may not work. Liu DW, Antzelevitch H25211. The absence of a prominent phase 1 or spike and dome morphology of the epicardial action potential is consistent with the absence of I to Figure 1as previously reported in the canine neonate [ 8 ]. Check out the forums and get free advice from the experts. Ricardinho New Member Member 4 posts. Once registered h2251 logged in, you will be able to create topics, post replies to existing threads, give reputation to your fellow members, get your own private messenger, post status updates, manage your profile and so much more.


Frequency-dependent effects of 4-aminopyridine and almokalant on action-potential duration of adult and neonatal rabbit ventricular muscle. In response to hyperpolarizing voltage clamp ey, the absolute magnitude of I K1 was much smaller in neonatal cells than adult myocytes.

Developmental changes in IKr and IKs contribute to age-related expression of dofetilide effects on repolarization and proarrhythmia.

Indeed, the I Kr inhibitor d-sotalol, causes a very significant prolongation of the action potential in neonate cells Figure 1. Hume JR, Uehara A. eet

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Author information Copyright and License information Disclaimer. The external solution contained in mM: The supernatant was filtered, centrifuged and the pellet containing the myocytes was stored in KB solution at room temperature. However, when I K1 was measured in neonate and adult ventricular cells, we found that the density of this current was greater in neonate cells compared to adults.


It is well established that prolongation of the QT interval can increase the risk for developing cardiac arrhythmias. Whole cell current data was acquired at kHz and filtered at 5 kHz. Isolated ventricular preparations Left ventricular tissues from epicardial, midmyocardial and endocardial regions approximately 1.

N Engl J Med.

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It is unclear whether the human myocardium exhibits these same differences. Isoproterenol and d-Sotalol were purchased from Sigma St.

Solutions All solutions were made with Milli-Q grade water. In the rat myocardium, the appearance of I to occurred at 2 weeks after birth[ 10 ]. You currently have javascript disabled. In addition, other experimental studies demonstrated that class III anti-arrhythmic agents produce a greater prolongation on action potential duration in the neonatal heart,[ 11 ] suggesting that the rapid and slow delayed rectifier currents are reduced in the young heart.

Remember me This is not recommended for shared computers. Jonathan M Cordeiro, Ph. There are no conflicts of interest to disclose.