Objective: To study the effects of total flavonoid from Scutellaria amoena on voltage-gated Na+ channels in cardiac tissues. Method: Adult guinea-pigs were heparinized and then sacrificed by decapitation after being anesthetized.The heart was removed immediately

and the aorta of the isolated heart was connected to a Langendorff apparatus and perfused with Ca2+-free Tyrode's solution for 10 min

and then with the same solution containing collagenase I.After dissociation and collection

cells were mechanically dispersed and single ventricular myocytes were enzymatically dissociated from adult guinea-pig heart.Voltage-dependent Na+ current was recorded using whole cell voltage-clamp technique. Result: Total flavonoid reversibly inhibited Na+ current with an IC50 value of 106 mg·L-1 (95% confidence range: 92-112 mg·L-1).The inhibitory effects of total flavonoid on Na+ current exhibited use-dependence.Total flavonoid at 106 mg·L-1 caused a negative shift (about 12 mV) in the voltage-dependence of steady-state inactivation of Na+ current

and retarded its recovery from inactivation

but did not affect its activation curve. Conclusion: In addition to blocking other voltage-gated ion channels

total flavonoid can block Na+ channels in guinea-pig ventricular myocytes.Total flavonoid acts as inactivation stabilizer of Na+ channels in cardiac tissues.