Figure 1.

(a) Representative monophasic action potential (MAP) recordings in perfused rabbit hearts during baseline and after the individual administration of HMR 1556 (100 nM), veratridine (125 nM) or dofetilide (7.5 nM) at a pacing cycle length (CL) of 500 ms. Endocardial MAP signals were obtained from the left ventricular apex. Amplitude of the MAP recordings was rescaled for the figure. The variability in MAP morphology and amplitude can be caused by changes in contact pressure between the MAP catheter and tissue, and do not necessarily reflect changes in specific ionic currents. Such variability is consistent with the known reported feature of MAP (Franz, 1999). (b) Individual effects of HMR 1556, veratridine or dofetilide on MAP duration at 90% repolarization (MAPD₉₀) at pacing CL of 500 ms. Mean±s.d., n=6. ^**P<0.01 vs untreated control.