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Related Experiment Videos

[The sinus node itself also plays a role in heart rate slowing down during postnatal development].

Zhi-Fang Yang1, Ci-Zhen Li, Qian Li

  • 1Department of Physiology, Shanghai Second Medical University, Shanghai 200025. liuyuanm@public6.sta.net.cn

Sheng Li Xue Bao : [Acta Physiologica Sinica]
|August 27, 2002
PubMed
Summary

As rabbits grow, their heart rate naturally slows due to changes in the sinus node (SN) cells. This involves a decreased depolarization rate and lower cAMP levels, impacting heart rate regulation.

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Area of Science:

  • Cardiovascular Physiology
  • Cardiac Electrophysiology

Background:

  • Heart rate typically decreases with age after birth.
  • Nervous and humoral factors are known regulators of heart rate.

Purpose of the Study:

  • To investigate the intrinsic mechanisms of heart rate slowing during postnatal growth.
  • To determine the role of sinus node (SN) cell automaticity in age-related heart rate changes.

Main Methods:

  • Isolated rabbit heart and SN preparations using Langendorff perfusion.
  • Microelectrode and perforated patch-clamp techniques to record pacemaker current I(f).
  • Radioimmunoassay to quantify intracellular cyclic adenosine monophosphate (cAMP) levels.

Main Results:

  • Spontaneous heart rate slowed with age in isolated preparations, independent of external factors.

Related Experiment Videos

  • A decreased rate of spontaneous phase 4 depolarization in SN cells was observed.
  • A negative shift in the threshold potential for I(f) and reduced SN cell cAMP concentration correlated with age.

    • Conclusions:

    • Intrinsic changes in SN cell automaticity contribute to age-related heart rate slowing.
    • Decreased I(f) threshold potential and reduced cAMP levels are potential mechanisms.
    • SN cell automaticity is a significant factor in heart rate regulation beyond nervous and humoral influences.