Effects of 2-[p-(dimethylamino) styryl] pyridine methiodide on action potentials of depolarized papillary muscle cells of guinea pig

Effects of 2-[p-(dimethylamino) styryl] pyridine methiodide (DSPM), nifedipine (Nif), CaCl2 and isoprenaline (Iso) on action potentials (AP) of guinea pig papillary muscle cells depolarized by high K+ (15.4 mmol/L) were studied by microelectrode technique. DSPM 45 mumols/L decreased the Vmaxf and Vmaxs of phasee O of the AP by 14 and 26%, respectively. APD90 was lengthened by 7%, amplitude of action potentials (APA) was decreased by 3%. The effects of CaCl2 on Vmaxs of phase 0 of the AP of depolarized papillary muscle cells were abolished by DSPM 45 mumols/L, but the effects of Iso were not antagonized. Effects of DSPM on Vmaxs of the AP of depolarized papillary muscle cells and the influence of DSPM to the action of CaCl2 and Iso were similar to those of Nif. It further suggests that DSPM may be a calcium antagonist.