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XB-ART-44425
Exp Clin Cardiol 2001 Jan 01;62:61-71.
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Potent and use-dependent block of cardiac sodium channels by U-50,488H, a benzeneacetamide kappa opioid receptor agonist.

Pugsley MK , Yu EJ , Goldin AL .


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To determine whether the kappa opioid receptor agonist U-50,488H, a benzacetamide derivative of the cyclo-hexane-1,2-diamine analgesics, may be a useful molecular probe to define the structural requirements of this class of drugs for cardiac sodium channel blockade. The electrophysiological effects of U-50,488H were compared with those of lidocaine, a clinically used class Ib antiarrhythmic agent, in rat heart sodium currents expressed in Xenopus laevis oocytes by using two-electrode voltage clamp. Both U-50,488H and lidocaine produced a concentration-dependent tonic block of sodium current, but U-50,488H was approximately fourfold more potent than lidocaine. Both drugs produced a hyperpolarizing shift in the voltage dependence of sodium channel inactivation and both delayed recovery from inactivation. Both drugs exhibited use-dependent block, but U-50,488H showed a 1.8-fold increase in potency compared with lidocaine at a high frequency of stimulation (30 Hz). The more potent tonic and use-dependent block of cardiac sodium channels by U-50,488H suggests that structural features of this molecule may provide it with a greater ability to block the channel. An understanding of these structural features may provide information needed in the development of novel arylacetamide-based antiarrhythmic drugs and insight into possible mechanisms describing channel block, resulting in a highly efficacious antiarrhythmic action in the heart.

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References [+] :
Bean, Lidocaine block of cardiac sodium channels. 1983, Pubmed