Effects Of ACH On Action Potential And Acetylcholine-sensitive Potassium Channel Currents In Lsolated Atrial Cells Of Guinea Pig

Vagus nerve function and the occurrence of a variety of arrhythmias is closely related,ACh as a transmitter of the vagus nerve,but also M receptor agonist,when Ach combination with the M receptor,resulting in negative chronotropic(heart rate), negative dromotropic(AV conduction slowing),and negative inotropic(atrial and ventricular contractile force to reduce).I hope this experiment by conventional glass micro-electrode and patch-clamp technique,further study of vagus nerve of the negative chronotropic,inotropic, dromotropic mechanism,that is,to explore acetylcholine(Ach) on isolated guinea pig atrial myocytes and its action potential the impact of ion channels.Using standard glass microelectrode technique in guinea pig atrial myocytes recorded action potentials.Thrusters used microelectrodes micro-electrodes inserted into atrial muscle cells,by stimulating the electrodes to stimulate the frequency of given 1Hz,wide wave of 2-4ms,2 times the threshold intensity of the current stimulus-driven samples,leads to action potential of atrial muscle.Observation of different concentrations of Ach 0.01 umol.L-1,0.1 umol.L-1,1umol.L-1 the action potential amplitude(APA),action potential repolarization 20%,50%,90%time (APD20,APD50,APD90) and effective refractory period(ERP) and refractory period dispersion(dERP) impact.Experimental results show that:①the control group for the APA action potential amplitude(97.17±8.93) mV;Ach0.01umol.L-1 group so that APA action potential decreased to(96.17±8.80) mV,there was no significant difference(p＞0.05);Ach 0.1 umol.L-1 group so that APA action potential decreased to(94.00±8.00) mV,there was no significant difference(p＞0.05);1 umol.L-1 group so that APA action potential decreased to(84.83±5.64) mV,there was a significant difference(p＜0.05).②from the experimental results can be seen,and compared with normal control group.0.01,0.1,1 umol/l Ach may shorten the APD(see Figure 1),were dose-dependent effect(see table 1).Action potential parameters of the control group APD20,APD50 and APD90 was(11.43±0.90) ms,(58.73±9.00) ms and(109.03±9.98) ms;Ach0.01umol.L-1 action potential parameters group APD20,APD50 and APD90 to(11.22±0.79) ms,(57.47±8.87) ms and(107.88±10.00) ms,there was no significant difference(p＞0.05); Ach 0.1 umol.L-1 action potential parameters group APD20,APD50 and APD90 for (10.68±0.62) ms,(52.02±6.24) ms and(103.42±9.36) ms,there was no significant difference(p＞0.05);Ach 1 umol.L-1 action potential parameters group APD20,APD50 and APD90 for(9.73±0.56) ms,(47.00±6.17) ms and(96.83±6.61) ms,there was a significant difference(p＜0.05).③Ach and dERP on the impact of ERP:ERP after intravenous infusion of Ach significantly lower than those in the control group(P＜0.05),Ach higher concentrations,ERP smaller difference between the concentrations were significantly(P＜0.05).Ach group dERP were significantly greater than the control group(P＜0.05),Ach higher concentration,dERP the greater the difference between the concentration of group was significant(P＜0.05,Table 1).Using whole-cell patch-clamp technique in guinea pig atrial myocytes Record acetylcholine-sensitive potassium current(IK_ACh),recorded at electrode extracellular add CdCl2(200umol/l) to block calcium current and calcium-activated,chloride current;with Glyburide(10umol/l) and the electrode within the liquid Mg-ATP (5mmol/l) to block ATP-sensitive potassium channels;chromanol 293B(20umol/l) and E-4031(5umol/l),respectively,Iks and Ikr channel blocker;4-AP,except Ito interference.Record of IK_ACh hyperpolarizing step program used:to maintain the potential of-40mV,test potential step from +40 mV to-120mV,step for-10mV,the duration of·300ms,can be recorded in guinea pig atrial myocytes IK_ACh current.. Then add different concentrations of acetylcholine,2min after the implementation of the program one time IK_ACh Record,Record Change two is defined as the current IK_ACh.Observation of different concentrations of Ach 0.01 umol.L-1,0.1 umol.L-1, 1 umol.L-1 on the impact of IK_ACh.The results showed that:IK_ACh for the control group(9.3±0.70) pA/pF;Ach0.01umol.L-1 so that action potentials IK_ACh group increased to(10.05±0.72) pA/pF,there was no significant difference(p＞0.05); Ach 0.1 umol.L-1 group increased so that action potentials IK_ACh to(11.69±2.13) pA/pF,there was a significant difference(p＜0.05);1 umol.L-1 group increased so that action potentials IK_ACh to(13.36±2.91) pA/pF,there is a significant difference (p＜0.01),into a dose-dependent manner.Through the current-voltage curve observed that the amplitude of Ach in addition to the current role has increased,the impact of other parameters did not.