| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Pharmacology, Columbia University, New York, New York 10032; and 2 Dipartimento di Fisiologia e Biochimica Generali, Elettrofisiologia, Università di Milano, 20133 Milano, Italy
Isolated newborn, but not adult,
rabbit sinoatrial node (SAN) cells exhibit spontaneous activity that
(unlike adult) are highly sensitive to the Na+ current
(INa) blocker TTX. To investigate this TTX
action on automaticity, cells were voltage clamped with ramp
depolarizations mimicking the pacemaker phase of spontaneous cells
(
60 to 20 mV, 35 mV/s). Ramps elicited a TTX-sensitive current in
newborn (peak density 0.89 ± 0.14 pA/pF, n = 24)
but not adult (n = 5) cells. When depolarizing ramps
were preceded by steplike depolarizations to mimic action potentials,
ramp current decreased 54.6 ± 8.0% (n = 3) but
was not abolished. Additional experiments demonstrated that ramp
current amplitude depended on the slope of the ramp and that TTX did
not alter steady-state holding current at pacemaker potentials. This
excluded a steady-state Na+ window component and suggested
a kinetic basis, which was investigated by measuring TTX-sensitive
INa during long step depolarizations. INa exhibited a slow but complete inactivation
time course at pacemaker voltages (
= 33.9 ± 3.9 ms at
50 mV), consistent with the rate-dependent ramp data. The data
indicate that owing to slow inactivation of INa
at diastolic potentials, a small TTX-sensitive current flows during the
diastolic depolarization in neonatal pacemaker myocytes.
sinoatrial node; slow inactivation; patch clamp
This article has been cited by other articles:
|
|
 |
|
  Y. Song, J. C. Shryock, and L. Belardinelli A slowly inactivating sodium current contributes to spontaneous diastolic depolarization of atrial myocytes Am J Physiol Heart Circ Physiol, October 1, 2009; 297(4): H1254 - H1262. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. E. Mangoni and J. Nargeot Genesis and Regulation of the Heart Automaticity Physiol Rev, July 1, 2008; 88(3): 919 - 982. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Baruscotti and R. B. Robinson Electrophysiology and pacemaker function of the developing sinoatrial node Am J Physiol Heart Circ Physiol, November 1, 2007; 293(5): H2613 - H2623. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Krogh-Madsen, P. Schaffer, A. D. Skriver, L. K. Taylor, B. Pelzmann, B. Koidl, and M. R. Guevara An ionic model for rhythmic activity in small clusters of embryonic chick ventricular cells Am J Physiol Heart Circ Physiol, July 1, 2005; 289(1): H398 - H413. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Rota and M. Vassalle Patch-clamp analysis in canine cardiac Purkinje cells of a novel sodium component in the pacemaker range J. Physiol., April 1, 2003; 548(1): 147 - 165. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Kurata, I. Hisatome, S. Imanishi, and T. Shibamoto Dynamical description of sinoatrial node pacemaking: improved mathematical model for primary pacemaker cell Am J Physiol Heart Circ Physiol, November 1, 2002; 283(5): H2074 - H2101. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. A. Papadatos, P. M. R. Wallerstein, C. E. G. Head, R. Ratcliff, P. A. Brady, K. Benndorf, R. C. Saumarez, A. E. O. Trezise, C. L.-H. Huang, J. I. Vandenberg, et al. Slowed conduction and ventricular tachycardia after targeted disruption of the cardiac sodium channel gene Scn5a PNAS, April 18, 2002; (2002) 82121299. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Protas, D. DiFrancesco, and R. B. Robinson L-type but not T-type calcium current changes during postnatal development in rabbit sinoatrial node Am J Physiol Heart Circ Physiol, September 1, 2001; 281(3): H1252 - H1259. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
