POSTSYNAPTIC ELECTROGENESIS IN SEPTATE GIANT AXONS .1. EARTHWORM MEDIAN GIANT AXON
POSTSYNAPTIC ELECTROGENESIS IN SEPTATE GIANT AXONS .1. EARTHWORM MEDIAN GIANT AXON
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DOI：
10.1152/jn.1957.20.6.553
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发表时间：
1957-01-01
影响因子：
2.5
通讯作者：
GRUNDFEST, H
中科院分区：
文献类型：
--
作者：
KAO, CY;GRUNDFEST, H
采用一个或几个细胞内微电极和神经索外记录，研究了蚯蚓中间巨轴突的分节、分隔活动。它的尖峰可以独立于2侧纤维的反应而被唤起，而后者的活动在正中巨轴突上不被电张力捕捉到。在适当的实验条件下，直接诱发的尖峰可能是一系列持续约10毫秒的小而梯度的电位。它们在轴突的不同部位的振幅和形式不同，并可能在不同的区域产生重复的尖峰。它们是突触后电位，可能是由神经索的其他纤维的活动引起的，这些活动激活了正中巨突触。中间纤维本身也能激发脊髓小纤维的活动，这种活动可以在大约40毫秒内被检测到。中间巨轴突的这些复杂的传出和传入突触连接与其节段起源有关，可能在动物的整合活动中起作用。轴突记录的突触后电位不是在间隔膜上产生的。本研究的证据，以及对小龙虾的隔侧巨大轴突进行的类似实验的其他更详细的发现，得出的结论是，隔仅仅是这些轴突不同部分的节段起源的个体发生的痕迹，可能由于膜阻力的减少而被修饰，并作为肾连接，没有活跃的连接转移，如突触电不可兴奋的突触后电位的发展。
One or several intracellular microelectrodes as well as external recording from the nerve cord were used to study the activity of the segmented, septate median giant axon of earthworm. Its spike can be evoked independently of responses in the 2 lateral fibers, and activity of the latter is not picked up electrotonically in the median giant axon. Under appropriate experimental conditions, the directly-evoked spike may be a sequence of small but graded potentials lasting up to about 10 msec. These differ in amplitude and form in different parts of the axon and may give rise at various regions to repetitive spikes. They are postsynaptic potentials probably evoked by activity of other fibers of the nerve cord which activate the median giant synaptically. The median fiber itself also excites activity in small fibers of the cord which can be detected for about 40 msec. These intricate efferent and afferent synaptic connections of the median giant axon, which are associated with its segmental origin, probably play a role in the inte-grative activity of the animal. The postsynaptic potentials recorded in the axons are not generated at the septal membranes. Evidence from the present studies, and other more detailed findings from similar experiments on the septate, lateral giant axons of crayfish lead to the conclusion that the septa are merely the ontogenetic vestiges of the segmental origin of the different parts of these axons, perhaps modified by diminished membrane resistance and behaving as ephatic junctions, without active junctional transfer such as occurs with the development of electrically inexcitable postsynaptic potentials at synapses.