Role of Individual Ionic Current Systems in the SA Node Hypothesized by a Model Study

• Sarai Nobuaki

  Department of Physiology and Biophysics, Kyoto University Graduate School of Medicine

• Matsuoka Satoshi

• Kuratomi Shinobu

• Ono Kyoichi

• Noma Akinori

Abstract

This paper discusses the development of a cardiac sinoatrial (SA) node pacemaker model. The model successfully reconstructs the experimental action potentials at various concentrations of external Ca²⁺ and K⁺. Increasing the amplitude of L-type Ca²⁺ current (I_CaL) prolongs the duration of the action potential and thereby slightly decreases the spontaneous rate. On the other hand, a negative voltage shift of I_CaL gating by a few mV markedly increases the spontaneous rate. When the amplitude of sustained inward current (I_st) is increased, the spontaneous rate is increased irrespective of the I_CaL amplitude. Increasing [Ca²⁺]_o shortens the action potential and increases the spontaneous rate. When the spontaneous activity is stopped by decreasing I_CaL amplitude, the resting potential is nearly constant (−35 mV) over 1–15 mM [K⁺]_o as observed in the experiment. This is because the conductance of the inward background non-selective cation current balances with the outward [K⁺]_o-dependent K⁺ conductance. The unique role of individual voltage- and time-dependent ion channels is clearly demonstrated and distinguished from that of the background current by calculating an instantaneous zero current potential ("lead potential") during the course of the spontaneous activity.<br>

Journal

• The Japanese Journal of Physiology

  The Japanese Journal of Physiology 53 (2), 125-134, 2003

  THE PHYSIOLOGICAL SOCIETY OF JAPAN

Keywords

• cardiac pacemaker model
• sinoatrial node
• sustained inward current
• L-type Ca²⁺ current
• delayed rectifier K⁺ current

Details

• CRID: 1390001205041420288
• NII Article ID: 10011229754
• NII Article ID: 130004435863
• NII Book ID: AA00691224
• DOI: 10.2170/jjphysiol.53.125
• COI: 1:STN:280:DC%2BD3szks1Ogsg%3D%3D
• ISSN: 18811396
• ISSN: 0021521X
• ISSN: http://id.crossref.org/issn/0021521X
• NDL BIB ID: 6610462
• PubMed: 12877768
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I6610462
• Web Site: https://search.jamas.or.jp/link/ui/2004037085
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • PubMed
  • CiNii Articles
• Abstract License Flag: Disallowed