M_3受体激动剂对豚鼠心室肌细胞L型钙通道的影响

目的研究M3受体激动剂胆碱对豚鼠心室肌细胞L型钙通道的影响。方法应用全细胞膜片钳技术记录M3受体激动剂胆碱对豚鼠单个心室肌细胞L型钙通道电流(ICa-L)的影响;采用激光扫描共聚焦技术观察细胞内钙离子的变化。结果应用10 mmol.L-1胆碱使豚鼠心室肌细胞ICa-L密度从(9.02±0.82)pA/pF减少到(5.61±0.55)pA/pF(n=4,P<0.01),5 nmol.L-14-DAMP能够使其恢复至(8.12±0.65)pA/pF(n=4,P<0.01);10 mmol.L-1胆碱抑制KCl除极诱导的心肌细胞内钙的升高,从(2.76±0.05)降至(1.37±0.05)倍(n=8,P<0.01),5 nmol.L-14-DAMP可以阻断该作用(n=8,P<0.01)。结论M3受体激动剂胆碱通过延长L型钙通道激活过程而明显抑制ICa-L,减少细胞外的钙离子内流,降低心肌细胞内钙,从而发挥抗心律失常作用。

Effects of M3 receptoRon L-type calcium current(ICa-L) in guinea pig ventriculaRmyocytes

Aim To investigate the effects of M3 receptor agonist choline on L-type calcium channels in guinea pig ventricular myocytes.Methods Whole cell patch clamp technique was used to record L-type calcium current.Laser scanning confocal microscope(LSCM) was employed to measure the concentration of intracellular free calcium.Results The application of 10 mmol·L-1 choline reduced the density of peak ICa-L from(9.02±0.82) pA/pF to(5.61±0.55)pA/pF(n=4,P<0.01).ICa-L came back to(8.12±0.65) pA/pF after the application of 5 nmol·L-1 4-DAMP.Choline remarkably shifted activation curve to the right,and delayed the voltage-dependent steady-state activation of calcium current.The half activation potential(V1/2) was(-18.62±1.14) mV in the control and(-21.40±1.12) mV in the presence of choline 10 mmol·L-1(n=6,P<0.05).Steady-state inactivation curve and the recovery time from inactivation were not affected markedly.LSCM recorded that KCl induced determined by used i increasing could be depressed by choline(10 mmol·L-1) and the effect of choline could be blocked by 4-DAMP(5 nmol·L-1).Conclusion Choline slows the activation procession of ICa-L and decreased i in ventricular myocytes will help its cardiac protection.