isolated single rabbit atrioventricular nodal myocytes (part 7)

RESULTS
Figure 1A shows the effects of flecainide 10 |iM. Under control conditions ICa,L in this myocyte had an amplitude of -625 pA. Within 1 min of applying this dose of the drug, Ica,L was reduced to -500 pA, after which no further effect of the drug was observed (this represented a 20% decline in control ICa,L amplitude). Flecainide also affected the INa elicited by the -40 mV conditioning pulse. In normal Tyrode’s solution INa was so large that it saturated the recording amplifier. After application of flecainide 10 |iM, the inward spike of INa was no longer off-scale, indicating that flecainide had partially inhibited INa. It was not possible to quantify the level of INa block (nor was this the aim of the present study), but this observation did suggest that while flecainide 10 |iM reduced ICa,L by only a small amount, this dose may have exerted a considerably larger blocking effect on INa. Figure 1B,C shows the effects of two other doses of flecainide (each applied to a different AVN myocyte).Flecainide 100 цМ blocked lNa almost completely but reduced Ica,L from -700 pA to -333 pA (a 52% decrease in Ica,L, Figure 1B)

Inhibition of L-type calcium current by flecainide in isolated single rabbit atrioventricular nodal myocytes You finally have a choice and can find yourself a perfectly reliable pharmacy to shop with for best medications available: buy diabetes drugs and see how quick and easy it could be to spend less money.

Figure 1 Flecainide blocks the L-type calcium current (Ica,l) in atrioventricular node myocytes. A Lower traces in right and left panels show voltage protocols, upper traces show the membrane current. A 100 ms prepulse was applied to -40 mV from a holding potential of -80 mV, followed by a 250 ms test pulse to +10 mV (pulse frequency 1 Hz). In control conditions (left panel), the prepulse to -40 mV elicited a large (off-scale) sodium current (Ino), which rapidly inactivated. The subsequent test pulse to +10 mV activated Ico,l. After application of 10 flecainide, the Ino amplitude was attenuated and lca,L was inhibited by 20%. B, C Current records (each from a different cell) showing the effects of flecainide 100 цM and 1 mM, respectively, on Ica,L (note also that both of these doses exerted profound blocking effects on Ino)  

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

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