Acidosis reduced frequency and [V.sub.max] (the maximal depolarization velocity) and shortened APD50 and APD90 (repolarization of AP at 50 and 90%) but did not influence the RP (resting potential) and APA (amplitude of AP) (Figures 1(c)-1(h)).
Lidocaine and Ni[Cl.sub.2] shortened APD50 more strongly than they did on APD90, suggesting minor effects of [I.sub.Na] and [I.sub.NCX] on the late phase of APD.
Representative traces of APs (c), mean values of resting potential (d), AP amplitude (e), maximal depolarization speed (f), APD50 (g), and APD90 (h) are shown.