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Related Experiment Videos

L-type but not T-type calcium current changes during postnatal development in rabbit sinoatrial node.

L Protas1, D DiFrancesco, R B Robinson

  • 1Department of Pharmacology, Columbia University, New York, New York 10032, USA.

American Journal of Physiology. Heart and Circulatory Physiology
|August 22, 2001
PubMed
Summary

Neonatal sinus node cells show slower rates when sodium current is blocked, suggesting a developmental shift. Adult sinus nodes exhibit a more negatively activating L-type calcium current, enhancing impulse initiation without sodium current.

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Area of Science:

  • Cardiovascular Physiology
  • Developmental Biology
  • Electrophysiology

Background:

  • Neonatal sinus node exhibits a faster intrinsic rate than adult sinus node.
  • Blockade of the sodium current (I(Na)) in neonatal sinus node cells results in a slower spontaneous rate compared to adult sinus node cells, indicating a potential developmental substitution of I(Na).

Purpose of the Study:

  • To investigate developmental changes in calcium currents, specifically T-type calcium current (I(Ca,T)) and L-type calcium current (I(Ca,L)), in rabbit sinus node cells.
  • To understand the functional role of these calcium currents in the developmental regulation of sinus node automaticity.

Main Methods:

  • Utilized ruptured and perforated patch clamp techniques to record calcium currents in sinus node cells from adult and newborn rabbits.

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  • Analyzed current density, voltage dependence of activation and inactivation, and recovery kinetics of I(Ca,T) and I(Ca,L).

    • Main Results:

    • I(Ca,T) density and voltage dependence remained unchanged between neonatal and adult sinus node cells.
    • Adult sinus node cells displayed a lower I(Ca,L) density compared to neonatal cells.
    • Significant shifts in the activation and inactivation midpoints of I(Ca,L) were observed, with adult cells showing more negative activation and less negative inactivation midpoints.
    • Recovery of I(Ca,L) from inactivation was slower in neonatal cells compared to adult cells.

    Conclusions:

    • The developmental changes in I(Ca,L), including its reduced density, more negative activation, and faster recovery in adults, may compensate for the absence of I(Na) in adult sinus node cells.
    • These alterations in I(Ca,L) contribute to the enhanced impulse initiation rate in adult sinus node cells.