Details

Autor(en) / Beteiligte

• Muramatsu, H
• Zou, A. R
• Berkowitz, G. A
• Nathan, R. D

Titel

Characterization of a TTX-sensitive Na+ current in pacemaker cells isolated from rabbit sinoatrial node

Ist Teil von

• American journal of physiology. Heart and circulatory physiology, 1996-06, Vol.270 (6), p.H2108-H2119

Ort / Verlag

United States

Erscheinungsjahr

1996

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• H. Muramatsu, A. R. Zou, G. A. Berkowitz and R. D. Nathan Department of Physiology, Texas Tech University Health Sciences Center, Lubbock 79430, USA. A tetrodotoxin (TTX)-sensitive Na+ current (iNa) was investigated in single pacemaker cells after 1-4 days in culture. Ruptured-patch and perforated-patch whole cell recording techniques were used to record iNa and spontaneous electrical activity, respectively. For seven cells exposed to 20 mM Na+ (22-24 degrees C) and held at -98 mV (25% of the channels inactivated), the uncorrected maximum iNa was -39 +/- 10 pA/pF at -29.1 +/- 2.4 (SE) mV, maximum conductance was 0.9 +/- 0.2 nS/pF (1.6 +/- 0.2 mS/cm2). Half-activation and inactivation potentials were -41.4 +/- 2.0 and -90.6 +/- 2.5 mV, and the corresponding slope factors were 6.0 +/- 0.4 and 6.4 +/- 0.6 mV. Inactivation and recovery from inactivation were best fit by sums of two exponentials. During action potential clamp, a TTX-sensitive compensation current accounted for 55% of the upstroke velocity. The results suggest that iNa contributes significantly to the action potential in some nodal pacemaker cells, and the characteristics of iNa are similar to those of atrial and ventricular myocytes.