乙酰胆碱对离体豚鼠心房肌动作电位及其脱敏的影响

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。

The effect ofacetylcholine on desensitization of action potential in guinea-pi gs atrial muscles

AIM: To investigate the mechanism underlying the effects of ACh on desensitization of action potential in guinea-pigs a t rial muscles. METHODS: Using standard microelectrodes and force tr ansducer we rec orded the effects and desensitization of ACh (0.01,0.1,1μmol/L) and blo ckers (such as atropine, CsCl) on the action potential duration(APD) and force c ontract ion 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 Ac h could not be blocked by 1 μmol/L atropine,20 mmol/L CsCl. But atropine or CsC l cou ld decrease the effect of shortening APD caused by ACh. CONCLUSION: T he effect of desensitization on APD to ACh in atrial cells is concentration-and time-dependent, these effects may be relate d to the change of the muscarinic receptor and the potassium channel.