rabbit atrioventricular nodal myocytes: DISCUSSION (part 4)

To our knowledge, the precise binding site or sites for fle-cainide on the L-type channel in cardiac cells have not yet been determined. In recent experiments using cloned neuronal calcium channel subunits, Zamponi et al investigated ICa,L block by flecainide and the structurally related compound fomocaine. By changing the concentration of barium (the permeant ion in their experiments) these workers observed that fomocaine block was sensitive to the external barium concentration, suggesting that fomacaine may act at a region of the channel readily accessible to the divalent permeant ion in the external solution. It remains to be determined whether the situation is similar in cardiac muscle cells; certainly, the rapid attainment of steady state block is consistent with sites readily accessible to externally applied fle-cainide.We did not observe a significant effect of flecainide on the voltage-dependent kinetics of ICa,L inactivation. For frog myocytes, Scamps et al reported a small hyper-polarizing shift of the steady state inactivation relation (up to -5 mV). At least in rabbit AVN myocytes, therefore, it appears that the dominant effect of flecainide is modulation of ICa,L amplitude, with a small effect on the voltage dependence of activation but without any significant change in voltage-dependent inactivation. It’s your turn to benefit from the shopping whenever you need efficient prednisone online that will be sure to work for your problem. This is now all very much possible at the best online pharmacy you have ever come across offering it services to you and other international customers interested.

Category: Antiarrhythmic agents Cardiology / Tags: Antiarrhythmic agents, Atrioventricular node, Flecainide, L-type calcium current, Single cell

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