Effect Of Zhigancao Decoction On Ion Channels In Rat Atrial Myocytes And Its Mechanism

Part 1 Literature study on the rule of traditional Chinese medicine in the treatment of atrial fibrillation based on Effect,Flavor and Meridian TropismObjective: To summarize and conclude the rules of traditional Chinese medicine in the treatment of atrial fibrillation from the aspects of property,flavor,channel tropism,functions and indicationsMethods: By searching the literature related to the treatment of atrial fibrillation on CNKI,Wanfang and Weipu databases,a database of the rules of the use of traditional Chinese medicine for atrial fibrillation was established after screening and standardized treatment,and data statistics and analysis were carried out on the recorded Chinese medicines by frequency analysis and cluster analysis.Results: It was found that in the treatment of atrial fibrillation,the most frequently used traditional Chinese medicines were sweet taste,clam nature,heart meridian and benefiting qi and nourishing yin.Conclusion:In the treatment of atrial fibrillation,traditional Chinese medicine mainly focuses on the methods of benefiting qi and nourishing yin,nourishing blood for tranquillization,which provides a theoretical basis for our study of zhigancao decoction,a prescription for benefiting qi and nourishing yin,and nourishing blood to repulse,in the treatment of atrial fibrillation.Part 2 Experimental study on effect of Zhigancao Decoction on ion channels in atrial myocytesObjective: To observe the effect of Zhigancao Decoction on the current,I-V curve and kinetics characteristics of L-type calcium channel and sodium channel in rat atrial myocytes,and to research the mechanism of action in the treatment of tachyarrhythmia.Method:Twenty-four SPF rats(male and female)were randomly divided into four groups: the low-dose group(1.125g/ml),the middle-dose group(2.25g/ml),the high-dose group(4.5g/ml)and the control group,with 6 rats in each group.The rats in the three groups were gavaged with the corresponding concentration of prepared Zhigancao decoction,and the rats in the control group were gavaged with the same volume of normal saline for 7 consecutive days.After the last administration for 1.5h,the rats were anesthetized and treated with anticoagulation,and then their hearts were quickly removed by surgery.Atrial myocytes of the rats in each group were acutely isolated by the retrograde enzymatic hydrolysis of the aorta under the Langendorff perfusion device.The whole-cell patch clamp technique was used to record the I-V curves and kinetics characteristics of ICa-Land INaof rat atrial myocytes in different groups.Results:(1)Effect of Zhigancao Decoction on ICa-Lof rat atrial myocytes:The ICa-Lclamping program was set in whole-cell patch clamp mode to guide the ICa-Lof atrial myocytes.The results showed that the ICa-Lpeak currents of rat atrial myocytes in the low-dose,medium-dose,and high-dose groups of Zhigancao Decoction compared with the control group(-11.57± 2.67)p A/p F,it decreased to(-10.17±2.78)p A/p F(P<0.05),(-6.97±2.45)p A/p F(P<0.01),(-7.31±2.09)p A/p F(P<0.01),and the IV curve were all shifted upward.Since there was no significant difference in the inhibitory degree of ICa-Lcurrent between the medium dose group and the high dose group(P>0.05),the medium dose group and the control group were choosen to campare their kinetics characteristics of ICa-L channel.The results showed that there was no significant difference in the activation curve and half activation voltage of atrial myocytes between the two groups(P>0.05).However,the homeostastic inactivation curve of the middle-dose drug group was shifted to the right,and the half deactivation voltage was increased(P<0.05).The curve of recovery after inactivation shifted downward,and the time constants(τ)was prolonged(P<0.01).(2)Effect of Zhigancao Decoction on INaof rat atrial myocytes:After the ICa-Lchannel was recorded,the clamping program was changed to record INachannel.The results showed that the INaof rat atrial myocytes in the low-dose,medium-dose,and high-dose groups of Zhigancao Decoction also decreased to(-42.14±4.76)p A/p F(P<0.05),(-36.52±1.76)p A/p F(P<0.01),(-34.76±3.58)p A/p F(P<0.01),and the I-V curves were all shifted up.The medium dose group and the control group were choosen to campare their kinetics characteristics of INachannel,the results showed that there was no significant difference in the activation curve and half activation voltage of atrial myocytes between the two groups(P>0.05).However,the homeostastic inactivation curve of the middle-dose drug group was shifted to the right,and the half deactivation voltage was increased(P<0.01).The curve of recovery after inactivation shifted downward,and the time constants(τ)was prolonged(P<0.01).Conclusion:1.125g/ml,2.25g/ml,4.5g/ml Zhigancao Decoction all have inhibitory effects on the currents of the ICa-Land INachannels of rat atrial myocytes,and the inhibitory effect is concentrationdependent.When choosing 2.25g/ml Zhigancao Decoction to compare the kinetic characteristics with the control group,it is found that it can slow down the inactivation speed and prolong the recovery time after inactivation of ICa-Land INachannels without affecting the peak potential,turnover potential,and activation curve.Thereby changing their kinetics characteristics,prolonging the action potential duration,and finally reaching the effect of slowing down the heart rate.This may be the mechanism of Zhigancao Decoction in the clinical treatment of atrial tachyarrhythmia.