REPOLARISATION ASSAYS

SINGLE VENTRICULAR MYOCYTES

EFFECTS OF NIFEDIPINE ON ACTION POTENTIAL DURATION

Figure 1 The effects of nifedipine on action potential duration.

Figure1   shows action potential records taken from a single left ventricular myocyte under our standard experimental conditions used for the action potential measurements in the absence (black) and presence (red) of nifedipine (1 é®�
Nifedipine (1, 10, 100 é £aused a concentration-dependent shortening of both APD₉₀ and APD₅₀ at 1 Hz.  The effects of nifedipine on APD are summarised in Figure 2.

Figure 2   Mean data for the effect of nifedipine on APD₅₀ and APD₉₀.

Figure 2    simple block of inward calcium current would be expected to shorten action potential duration, and this was tested under the conditions of the present experiments using nifedipine. As expected, nifedipine caused a concentration-dependent shortening of both APD₅₀ and APD₉₀. The effects on APD₅₀ appeared to be slightly greater than those on APD₉₀.
No statistically significant changes were detected in MRD.