The non-impulsive stretch-receptor complex of the crab: a study of depolarization--release coupling at a tonic sensorimotor synapse.
The non-impulsive stretch-receptor complex of the crab: a study of depolarization--release coupling at a tonic sensorimotor synapse.
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螃蟹的非冲动拉伸感受器复合体：强直感觉运动突触的去极化-释放耦合研究。
DOI：
10.1098/rstb.1980.0092
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
Llinás,R
中科院分区：
文献类型：
--
作者：
Blight,AR;Llinás,R
本文报道了一种用于研究突触传递的新方法--中华蟹胸神经节。本文用细胞内钴染色和光镜、电子显微镜研究了胸髋关节非冲动牵张感受器神经元及其与之形成突触连接的促进型运动神经元的中枢解剖。注意力集中在伸展感受器T纤维与供应启动肌的四个大运动神经元之间的相互作用上，这些启动肌的胞体位于神经节的背面。T纤维突触前终末区呈圆柱形，直径40~60μm，周围有大量突触小泡，与运动神经元树突复合体相对。用蔗糖间隙跨膜电流注入分离的T纤维，并用突触前终末和突触后细胞胞体微电极同步记录的方法，研究了受体细胞和运动神经元之间的连接传递特性。结果表明，T纤维中的去极化-释放耦合具有与鱿鱼巨型突触相似的特性，具有相同的阈值、峰值释放和抑制电位。螃蟹的突触与鱿鱼的不同之处在于，它们通常传输从外周递减传导的长时间、渐变的去极化(即受体电位)。与这一作用一致的是，研究发现，这些连接能够持续数秒的紧张性传递，而不会像更多时相突触那样出现强烈的耗尽。在对突触特性和牵拉反射之间关系的研究中发现，总反射的一些时间和幅度依赖的行为可以在突触传递的水平上编码，主要是通过递质可用性的参数。电信号在感觉纤维的近端和突触前部分的传导也被研究。对纤维中阶跃去极化电流的瞬时响应表明存在一种机制，用于部分补偿递减传导的受体电位中的电容失真。这是第一个从非脉冲神经元的突触前终末进行细胞内记录并同时监测突触后电位变化的例子，允许直接分析去极化-释放耦合特性。讨论了为进一步研究突触生理和感觉运动系统所做的准备工作。
A new preparation for the study of synaptic transmission is described from the thoracic ganglion of the crabCallinectes sapidus. The central anatomy of the nonimpulsive stretch-receptor neurons of the thoracic-coxal joint and that of the promotor motoneurons with which they form synaptic junctions was studied with intracellular cobalt staining and light and electron microscopy. Attention was centred on the interaction of the stretch-receptor T-fibre and the four large motoneurons supplying the promotor muscle which have their cell-bodies on the dorsal surface of the ganglion. The presynaptic terminal region of the T-fibre appeared to be a simple cylinder in form with a diameter of 40-60 μm and containing large stores of synaptic vesicles at its periphery, opposite the complex of motoneuron dendrites. The transmission characteristics of the junctions between receptor cell and motoneurons were studied by transmembrane current injection into the isolated T-fibre by means of a sucrose gap and simultaneous intracellular recording with microelectrodes from the presynaptic terminal and the somata of postsynaptic cells. It was shown that depolarization-release coupling in the T-fibre has similar properties to those that have been demonstrated in the squid giant synapse, with the same values for ‘threshold’, peak release and ‘suppression potential’. The crab synapses differ from that of the squid in that they normally transmit prolonged, graded depolarizations (i.e. receptor potentials) which are decrementally conducted from the periphery. Consistent with this role, the junctions were found to be capable of continuous tonic transmission over many seconds without the strong depletion seen in more phasic synapses. In a study of the relation between the synaptic properties and the stretch reflex it was shown that some of the time- and amplitude-dependent behaviour of the overall reflex can be encoded at the level of the synaptic transmission, largely through the parameter of transmitter availability. Conduction of electrical signals in the proximal and presynaptic part of the sensory fibre was also investigated. Transient responses to step depolarizing currents in the fibre indicate the existence of a mechanism for the partial compensation of capacitative distortion in the decrementally conducted receptor potential. This is the first example of intracellular recording from presynaptic terminals of nonimpulsive neurons with simultaneous monitoring of postsynaptic potential changes, allowing for a direct analysis of depolarization-release coupling characteristics. The use of the preparation for further study of synaptic physiology and sensorimotor systems is discussed.