Abstract: Ventricular myocardiocytes from neonatal Wistar rats were isolated and cultured.Aconitine,Ca²⁺ channel blocker verapamil or Ca²⁺ channel activator BAY K8644 were added to thebath solution separately. Using the cell-attached configuration of the patch clamp technique ,the singlechannel activities of L type Ca²⁺ channel were recorded before and after addition of all three drugs.The results showed the blocking effect of aconitine (50μg· ml-1)on L type Ca²⁺ channels. Itsmechanism may be relevant to the decrease in both open state probability and the mean open time ofCa²⁺ channel. The difference was statistically significant compared with control group(P<0.01).The amplitude of Ba²⁺ currents ,which flow through open L type Ca²⁺ channel was unchanged.