MULTIPLE SITES OF SPIKE INITIATION IN A SINGLE DENDRITIC SYSTEM
MULTIPLE SITES OF SPIKE INITIATION IN A SINGLE DENDRITIC SYSTEM
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DOI：
10.1016/0006-8993(74)90612-x
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发表时间：
1974-01-01
期刊：
影响因子：
2.9
通讯作者：
KENNEDY, D
中科院分区：
文献类型：
--
作者：
CALABRESE, RL;KENNEDY, D
小龙虾多节触觉中间神经元（MTIs）提供了一个独特且令人信服的例证，即单个中枢神经元中存在多个轴突尖峰起始区。这些发现对其他神经元系统的影响在很大程度上被忽视了；每个起始区与单独的神经节神经丛的关联允许这种现象被忽略为仅在具有梯状神经索的无脊椎动物中发现的好奇心1。在单个树突乔木内已证明多个尖峰起始区的中枢神经元的所有情况下（例如，鳄鱼小脑的浦肯野细胞，9，猫海马的锥体细胞，蟹眼柄运动神经元lZ， 1~和小龙虾快速屈肌运动神经元15)，树突尖峰仅对主轴突尖峰起始区提供阈下兴奋。这种树突尖峰不会传播到轴突中，因为它们必须穿过低安全系数的区域，其功能与具有大树突树（例如，浦肯野细胞 s，9）或小（例如，蟹眼柄运动神经元 12，~ 3）直径树突的神经元中的经典突触后电位相同。然而，一些神经元有迹象表明，树突尖峰可能可以到达轴突。在未成熟的猫新皮质神经元和已诱发癫痫发作的成年猫的海马神经元中，树突尖峰经常主动侵入索马里浦肯野细胞中的一些树突尖峰无故障地传导至轴突 s, 9，而在鱼的动眼神经元中，放电水平差异表明一些主动侵入轴突的尖峰可能在远离主轴突部位的部位启动。感受野在单个树突乔木内有多个尖峰起始区，并且每个都可以直接进入轴突。此外，我们发现这些尖峰起始区域相距甚远，以至于它们不能受到阈下 EPSP 的共同影响。小龙虾（克氏原螯虾）的腹部神经系统是从动物中分离出来的，除了它通过第六腹部神经节的第四根和（有时）第五根与尾节的触觉毛发受体相连。这些根几乎完全是感觉性的，代表了许多有效的兴奋途径。
Crayfish multisegmental tactile interneurons (MTIs) provide a unique and convincing illustration that multiple axonal spike-initiating zones exist in individual central neuronsL The implications of these findings for other neuronal systems have largely been ignored; the association of each initiating zone with a separate ganglionic neuropile allows the phenomenon to be dismissed as a curiosity found only in invertebrates with ladder-like nerve cords 1. In all cases of central neurons in which multiple spike-initiating zones have been demonstrated within a single dendritic arbor (eg, Purkinje ceils of alligator cerebellumS, 9, pyramidal cells of cat hippocampus, crab eye stalk motor neuronslZ, 1~, and crayfish fast flexor motor neurons15), the dendritic spikes contribute only subthreshold excitation to a main axonal spike initiating zone. Such dendritic spikes, which do not propagate into the axon because they must traverse regions of low safety factor, serve the same function as classical postsynaptic potentials in neurons with large dendritic trees (eg, Purkinje cells s, 9) or small (eg, crab eye stalk motor neuronsl2,~ 3) diameter dendrites. There are indications in some neurons, however, that dendrite spikes may have access to the axon. In immature cat neocortical neurons and the hippocampal neurons of adult cats in which seizures have been induced, dendritic spikes often actively invade the somalL Some dendritic spikes in Purkinje cells are conducted to the axon without failure s, 9 and in fish oculomotor neurons, firing level differences indicate that some spikes that actively invade the axon may be initiated at sites distant from the main axonal site v. We here report that the crayfish MTIs with bilateral receptive fields have multiple spike-initiating zones within a single dendritic arbor, and that each has direct access to the axon. Moreover, we show that these spike-initiating zones are so widely separated that they cannot be jointly influenced by subthreshold EPSPs. The abdominal nervous system of the crayfish (Procambarus clarkii) was isolated from the animal except for its connection to the tactile hair receptors of the telson via the fourth and (sometimes) the fifth roots of the sixth abdominal ganglion. These roots are almost exclusively sensory and represent potent excitatory pathways for a number