Electrophysiologic effect of dipfluzine on pacemaker cells in sinoatrial node of rabbits

The effect of dipfluzine(3-30 μmol·L 1 ) on the electrical characteristics of pacemaker cells in sinoatrial node(SAN) of rabbits was studied using intracellular microelectrode technique. The results showed that dipfluzine reduced amplitude of action potential(APA), maximal rate of depolarization in phase 0( max ), velocity of diastolic (phase 4) depolarization (VDD) and rate of pacemaker firing (RPF) in SAN pacemaker cells in a concentration dependent manner, but had no significant effect on maximal diastolic potential, and duration of 50% repolarization in the concentrations used. Dipfluzine significantly inhibited high Ca 2+ (4 mmol·L 1 ) or Bay K8644(0.5 μmol·L 1 ) raised VDD and RPF. It is suggested that dipfluzine reduce APA, [AKV·5] max , VDD and RPF in SAN pacemaker cells in higher concentrations, which may be attributed to the decrease in Ca 2+ influx.