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  • Title: Lidocaine blocks open and inactivated cardiac sodium channels.
    Author: Matsubara T, Clarkson C, Hondeghem L.
    Journal: Naunyn Schmiedebergs Arch Pharmacol; 1987 Aug; 336(2):224-31. PubMed ID: 2446150.
    Abstract:
    Guinea-pig papillary muscles were voltage-clamped using the single sucrose gap technique. The maximum upstroke velocity of the action potential (Vmax) was used as an indicator of the sodium conductance. Lidocaine (5 mumol/l to 40 mumol/l) reduced Vmax in a use-dependent fashion. Block of sodium channels developed during channel opening and while the channels were inactivated. Block of inactivated channels was not voltage-dependent over the -40 mV to +40 mV range. Recovery from block occurs upon repolarization, and for a given diastolic interval the recovery is more complete as the membrane potential is hyperpolarized over the -80 mV to -150 mV range. These results can be accounted for in terms of the modulated receptor hypothesis, where lidocaine has a low affinity for rested sodium channels, but a high affinity for open and inactivated channels.
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