The Effects Of Haloperidol On Action Potential Of The Rabbit Left Ventricular Purkinje Fibers In Vitro

Aim: To study the effects of Haloperidol on action potential of the rabbit left ventricular Purkinje fibers in vitro.Methods: Standard intracellular microelectrode technique is used to observe the effects of Haloperidol on the action potential parameters including APA, Vmax, APD₅₀ and APD₉₀ in rabbit Purkinje fibers under following conditions: a given stimulation while the treatment of different concentrations of Haloperidol (0.01,0.03,0.1,0.3,1,3,10μM); a fixed Haloperidol concentration (0.3μM or 3μM) treatment yet stimulation with varying frequencies (30,60,90,120,150,180bpm)Results: With the increase of the concentration, a gradual prolongation in APD₉₀ by Haloperidol was observed, which was more pronounced at 1μM,after that,the extent of the prolongation in APD₉₀ decreased gradually. Prolongation in APD₅₀ was first observed when the concentration was 0.01μM and beginning from 1uM APD₅₀ was shortened. In general, there was a trend for prolongation followed with a shortening. A gradual decrease in Vmax was observed starting from the concentration at 0.01μM and was significant starting from the concentration at 0.1μM.With the decrease of frequency, the prolongation of APD₉₀ induced by Haloperidol with fixed concentration was more obvious than before, and a marked prolongation was seen at 30bpm and 60bpm. Haloperidol slightly prolonged APD₅₀. With the increase of frequency,the effect of Haloperidol on Vmax was depressed, which more pronounced ?n faster stimulating frequencies than that of slower stimulating frequencies. Comparing the effects of Haloperidol (0.3μM and 3μM) onaction potential of rabbit cardiac Purkinje fibers under different frequencies, we observed that higher concentration of Haloperidol showed a more apparent decline in Vmax and APA than that of lower concentration while APD90 prolongation was more obvious with the lower concentration. Haloperidol with higher concentration shortened APD50 slightly which complies with the result of the previous test.Conclusion: Haloperidol can prolong APD (especially APD9o)and depresses Vmax in isolated rabbit cardiac Purkinje fibers, and this effect is related to the dose of Haloperidol and the stimulating frequency.