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Type: Journal article
Title: Interaction of lidocaine with the cardiac sodium channel Effects of low extracellular pH are consistent with an external blocking site
Author: Tan, H.
Saint, D.
Citation: Life Sciences, 2000; 67(22):2759-2766
Publisher: Pergamon-Elsevier Science Ltd
Issue Date: 2000
ISSN: 0024-3205
Abstract: Brief extracellular application of millimolar concentrations of lidocaine affected sodium currents recorded in isolated rat ventricular myocytes in two ways: 1) a reduction of the maximum current consistent with a channel blocking action, and 2) a negative shift in the voltage dependence of inactivation consistent with an interaction with the inactivated state of the channel. Both effects occurred very rapidly (<< 1 s). Decreasing extracellular pH to 6.4 increased the potency for channel block (EC50 1.8 +/- 0.2 mM at pH 7.4 and 0.8 +/- 0.1 mM at pH 6.5) and decreased the potency to shift inactivation (V(1/2) shift -42 mV by 1 mM lidocaine at pH 7.4 and -12.6 mV at pH 6.5). Channel block was slightly less at +90 mV compared to -40 mV at either pH (not statistically significant). The increase in potency for block at decreased extracellular pH, while intracellular pH is buffered, and the lack of voltage dependence of block, suggest that the charged form of lidocaine can block the channel by interacting with a site near the extracellular mouth, although alternative explanations are discussed.
Keywords: Myocardium; Heart; Heart Ventricles; Animals; Rats; Rats, Wistar; Lidocaine; Sodium Channels; Sodium Channel Blockers; Evoked Potentials; Hydrogen-Ion Concentration; Male; In Vitro Techniques
RMID: 0001001650
DOI: 10.1016/S0024-3205(00)00855-9
Appears in Collections:Physiology publications

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