The distribution of acetylcholine sensitivity at the post‐synaptic membrane of vertebrate skeletal twitch muscles: iontophoretic mapping in the micron range.
The distribution of acetylcholine sensitivity at the post‐synaptic membrane of vertebrate skeletal twitch muscles: iontophoretic mapping in the micron range.
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脊椎动物骨骼抽搐肌突触后膜乙酰胆碱敏感性的分布：微米范围内的离子电渗映射。
DOI：
10.1113/jphysiol.1975.sp010821
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发表时间：
1975
期刊：
影响因子：
--
通讯作者：
D. Yoshikami
中科院分区：
文献类型：
--
作者：
S. W. Kuffler;D. Yoshikami
1. 用离子电泳方法在蛇、蛙和泥鳅的骨骼肌中绘制了乙酰胆碱（ACh）的敏感性分布，该方法在mum范围内提供了分辨率。2. 这些制备物是薄薄的肌肉纤维薄片，用诺马尔斯基光学观察，可以清晰地看到细胞的细节。蛇的肌肉特别适合。它们的运动神经终止于紧致的一簇突触钮扣，这些钮扣位于肌肉表面不同的凹坑中。用胶原酶治疗后，运动神经及其末端钮扣可以被移除，暴露出突触下膜。3. 离子电泳应用ACh获得的剂量响应曲线斜率以mV/nC表示，并作为ACh敏感性的指标。无论是在保留或移除终端的情况下，测试中灵敏度最高的区域都是紧挨着突触前终端的区域。最大的亚突触敏感性约为5000 mV/nC， ACh释放引起的电位的时间过程与神经释放的ACh建立的突触电位的时间过程具有密切的相关性。4. 突触外膜的灵敏度比突触下膜低至少50倍。低的突触外敏感性在更远的距离上进一步下降。5. 乙酰胆碱酯酶在生理学上被证明局限于突触亚区。在距突触边缘约2 μ m的突触外区域未检测到该酶的活性。6. 高密度的受体和乙酰胆碱酯酶被限制在肌肉的突触下层膜上也是副交感神经细胞的一个特征。这表明类似的专门化可能是具有化学突触的神经元的普遍特性。
1. The distribution of acetylcholine (ACh) sensitivity was mapped in skeletal twitch muscles of the snake, frog and mudpuppy with iontophoretic methods that provide a resolution in the mum range. 2. The preparations were thin sheets of muscle fibres that were viewed with Nomarski optics, giving sharp definition of cellular detail. The muscles in the snake were especially suitable. Their motor nerves terminate in a compact cluster of synaptic boutons that rest in distinct craters on the muscle surface. After treatment with collagenase the motor nerve and its terminal boutons can be removed, exposing the subsynaptic membrane in the craters. 3. The slopes of dose‐response curves obtained by iontophoretic application of ACh were expressed in mV/nC and used as an index of ACh sensitivity. The areas of highest sensitivity, tested either with the terminals in place or removed, were those immediately under the presynaptic terminals. The greatest subsynaptic sensitivities were about 5000 mV/nC, and the time course of the potentials caused by ACh released iontophoretically closely matched that of synaptic potentials set up by ACh released by the nerve. 4. The sensitivity of the extrasynaptic surface less than 2 mum away was at least 50 times lower than that of the subsynaptic membrane. The low extrasynaptic sensitivity declined still further at greater distances. 5. Acetylcholinesterase was shown physiologically to be confined to subsynaptic areas. No activity of the enzyme was detected in extrasynaptic areas beyond about 2 mum from the edge of the synapse. 6. The confinement of high densities of receptors and of acetylcholinesterase to the subsynaptic membrane in muscles is also a feature in parasympathetic neurones. It is suggested that similar specialization may be a widespread property of neurones with chemical synapses.