|
|
||||||||
Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario, Canada M5G 1L7
We examined the
ability of local anesthetics to correct altered inactivation properties
of rat skeletal muscle Na+
channels containing the equine hyperkalemic periodic paralysis (eqHPP)
mutation when expressed in Xenopus
oocytes. Increased time constants of current decay in eqHPP channels
compared with wild-type channels were restored by 1 mM benzocaine but
were not altered by lidocaine or mexiletine. Inactivation curves, which were determined by measuring the dependence of the relative peak current amplitude after depolarization to
10 mV on conditioning prepulse voltages, could be shifted in eqHPP channels back toward that
observed for wild-type (WT) channels using selected concentrations of
benzocaine, lidocaine, and mexiletine. Recovery from inactivation at
80 mV (50-ms conditioning pulse) in eqHPP channels followed a
monoexponential time course and was markedly accelerated compared with
wild-type channels (
WT = 10.8 ± 0.9 ms;
eqHPP = 2.9 ± 0.4 ms). Benzocaine slowed the time course of recovery
(
eqHPP,ben = 9.6 ± 0.4 ms
at 1 mM) in a concentration-dependent manner. In contrast, the recovery
from inactivation with lidocaine and mexiletine had a fast component
(
fast,lid = 3.2 ± 0.2 ms;
fast,mex = 3.1 ± 0.2 ms),
which was identical to the recovery in eqHPP channels without drug, and
a slow component (
slow,lid = 1,688 ± 180 ms;
slow,mex = 2,323 ± 328 ms). The time constant of the slow component of the
recovery from inactivation was independent of the drug concentration,
whereas the fraction of current recovering slowly depended on drug
concentrations and conditioning pulse durations. Our results show that
local anesthetics are generally incapable of fully restoring normal WT
behavior in inactivation-deficient eqHPP channels.
sodium channel; inactivation
This article has been cited by other articles:
![]() |
W. Ulbricht Sodium Channel Inactivation: Molecular Determinants and Modulation Physiol Rev, October 1, 2005; 85(4): 1271 - 1301. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. E. Bondarenko, G. C. L. Bett, and R. L. Rasmusson A model of graded calcium release and L-type Ca2+ channel inactivation in cardiac muscle Am J Physiol Heart Circ Physiol, March 1, 2004; 286(3): H1154 - H1169. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. A. Li, R. G. Tsushima, K. Himmeldirk, D. S. Dime, and P. H. Backx Local Anesthetic Anchoring to Cardiac Sodium Channels : Implications Into Tissue-Selective Drug Targeting Circ. Res., July 9, 1999; 85(1): 88 - 98. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |