摘要
目的 :探讨迷走神经递质乙酰胆碱 (ACh)对家兔窦房结细胞动作电位、毒蕈碱型钾离子流 (IK,ACh)、钙离子流(ICa)及超极化激活的离子流 (If)的影响及脱敏可能的离子机制。方法 :采用全细胞膜片钳技术分别记录了单个家兔窦房结细胞的各种通道离子流及动作电位。结果 :1当给单个心脏窦房结细胞灌注 ACh时 ,可使其自发电活动减慢 ,甚至消失。而当持续灌注 ACh时 ,可出现其负性变率作用的脱敏现象 ,即尽管 ACh持续存在 ,窦房结细胞的自发电活动逐渐恢复。 2 ACh可以激活 IK,ACh,IK,ACh随着 ACh的持续灌注可出现脱敏现象。 3ACh对“基础”钙离子流 (ICa)无明显作用 ,但当钙离子流被 β受体激动剂异丙肾上腺素增大之后 ,ACh可以降低此钙通道离子流。ACh的作用并未出现脱敏现象。 4ACh可以降低单个窦房结细胞的超极化激活的离子流 (If)。这个效应也没有脱敏的现象。结论 :ACh对心脏所致的负性变率作用的脱敏现象主要是毒蕈碱型钾通道 IK,ACh脱敏的缘故。
AIM:To investigate the effects and mechanism of acetylcholine(ACh) on desensitization of action potential,calcium current(I Ca ),the hyperpolarization activated current(I f) and ACh induced potassium current (I K,ACh ) in rabbit sinoatrial node cells. METHODS:We were using the whole cell patch clamp techniques to record the various ion currents and action potentials in single sinoatrial mode cells isolated from rabbit hearts. RESULTS:①We observed that the activation of the channel by ACh results in a slowing down or cease of the spontaneous activity in single sinoatrial node cells. During an exposure to ACh the negative chronotropic effect of ACh fades and the spontaneous activity resumed despite the continuous presence of ACh. ② Ach activated an inward rectifying potassium current (I K,ACh ), which faded in the continuous presence of ACh. ③ACh had no effect on “basal” L type calcium current, but ACh decreased I Ca , which had been potentiated by β agonist, isoprenaline. This effect did not fade during exposure to ACh. ④ACh decreased I f current and this effect again did not fade. CONCLUSION:Desensitization of negative chronotropic response to ACh is mostly the result of fade of I K,ACh .
出处
《心脏杂志》
CAS
2001年第2期81-83,86,共4页
Chinese Heart Journal
基金
国家自然科学基金资助项目!( 3 9870 3 3 4
3 9970 2 73 )
关键词
离子通道
乙酰胆碱
窦房结细胞
脱敏
ion channels
acetylcholine
sinoatrial node cells
desensitization
