Presynaptic muscarinic inhibition in bullfrog sympathetic ganglia.
Presynaptic muscarinic inhibition in bullfrog sympathetic ganglia.
复制标题
牛蛙交感神经节的突触前毒蕈碱抑制。
DOI：
10.1113/jphysiol.1996.sp021225
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Horn,JP
中科院分区：
文献类型：
--
作者：
Shen,WX;Horn,JP
1. 通过记录牛蛙B、C神经元突触电流，研究毒蕈碱对交感神经节烟碱传递的调节作用。2. 用电碱可使B神经元在< 0.2 Hz时记录的EPSCs振幅降低57%。作用可逆，无明显脱敏，EC50为102 nM。毒蕈碱对C神经元的EPSCs无影响。3. 毒蕈碱对乙酰胆碱对B神经元离子电泳引起的电流没有影响。毒蕈碱增加了EPSC振幅变异系数（c.v）。对c.v.2对照与c.v.2毒蕈碱比值的影响与EPSC平均振幅的变化成正比。4. 通过比较正常林格氏液和阿托品中的EPSCs，观察神经末梢乙酰胆碱对毒蕈碱受体的激活作用。当频率从1 Hz增加到5 Hz时，EPSC幅度被抑制了15‐40%。抑制开始的最小潜伏期约为2秒。20 Hz的刺激没有产生抑制作用。5. 结果表明，突触前毒蕈碱受体可通过节前交感神经末梢的一个功能亚类选择性表达。受体的生理激活发生在重复活动中。自身受体介导的抑制程度随刺激频率的双相函数而变化。
1. Muscarinic modulation of nicotinic transmission was studied in bullfrog sympathetic ganglia by recording synaptic currents from B and C neurones. 2. Bath‐applied muscarine reduced the amplitude of EPSCs recorded at < 0.2 Hz from B neurones by up to 57%. The action was reversible, showed no apparent desensitization, and had an EC50 of 102 nM. Muscarine had no effect on EPSCs in C neurones. 3. Currents evoked by ionophoretic application of ACh to B neurones were unchanged by muscarine. Muscarine increased the coefficient of variation (c.v.) of EPSC amplitude. The effect upon the ratio of c.v.2control to c.v.2muscarine was proportional to the change in mean EPSC amplitude. 4. Activation of muscarinic receptors by ACh from nerve terminals was observed by comparing trains of EPSCs in normal Ringer solution and atropine. Inhibition of EPSC amplitude by 15‐40% was seen as frequency was increased from 1 to 5 Hz. The minimal latency for onset of inhibition was approximately 2 s. Stimulation at 20 Hz did not produce inhibition. 5. The results indicate that presynaptic muscarinic receptors are selectively expressed by a functional subclass of preganglionic sympathetic nerve terminals. Physiological activation of the receptors occurs during repetitive activity. The extent of autoreceptor‐mediated inhibition varies as a biphasic function of stimulus frequency.