乙酰胆碱对离体豚鼠心房肌动作电位及其脱敏的影响

The effect of acetylcholine on desensitization of action potential in guinea-pigs atrial muscles

目的 :研究迷走神经递质乙酰胆碱 (ACh)对离体豚鼠心房肌细胞动作电位 (AP)的影响及其对心房肌的脱敏 ,探讨脱敏可能发生的机制。方法 :采用标准玻璃微电极细胞内记录方法 ,观察不同浓度 (0 .0 1,0 .1,1μm ol/ L) ACh对心房肌细胞 AP的影响及对动作电位时程 (APD)和收缩力的脱敏现象 ,并观察了受体或通道水平的阻断剂阿托品、氯化铯 (Cs Cl)对 ACh所致的心房肌 APD脱敏的影响。结果 :10 .0 1,0 .1,1μm ol/ L ACh分别缩短 APD的变化率为 (6 .0 2± 1.0 4) % ,(14.2 0± 3.79) % ,(30 .2 0± 3.6 5 ) %。 2 0 .0 1μmol/ L ACh对心房肌细胞没有脱敏 ;0 .1μm ol/ L ACh对心房肌细胞 APD有轻微脱敏 ,脱敏持续时间为 1m in;而 1μmol/ L ACh对心房肌细胞 APD脱敏明显 ,脱敏持续时间为 5 m in。 31μmol/ L 阿托品与 2 0 m mol/ L Cs Cl并不能阻断 1μmol/ L ACh对心房肌细胞APD的脱敏。结论 :ACh缩短 APD的作用随浓度增大而增大 ;ACh对离体豚鼠心房肌细胞 APD的脱敏有浓度依赖性与时间依赖性 ;脱敏的发生可能与毒蕈碱型胆碱能受体及 Ik,ACh电流有关。

AIM: To investigate the mechanism underlying the effects of ACh on desensitization of action potential in guinea pigs atrial muscles. METHODS: Using standard microelectrodes and force transducer we recorded the effects and desensitization of ACh (0.01,0.1,1μmol/L) and blockers (such as atropine, CsCl) on the action potential duration(APD) and force contraction in atrial muscles. RESULTS:①0.01,0.1,1μmol/L ACh shortened the APD by (6.02±1.04)%,(14.20±3.79)% and (30.20±3.65)% respectively. ②0.01μmol/L ACh has no desensitization and the time of desensitization at 0.1 and 1 μmol/L ACh lasted 1 min and 5 min, respectively. ③The desensitization at 1 μmol/L Ach could not be blocked by 1 μmol/L atropine,20 mmol/L CsCl. But atropine or CsCl could decrease the effect of shortening APD caused by ACh. CONCLUSION: The effect of desensitization on APD to ACh in atrial cells is concentration and time dependent, these effects may be related to the change of the muscarinic receptor and the potassium channel.