The origin of rhythmic fast subthreshold depolarizations in thalamic relay cells of rats under urethane anaesthesia
The origin of rhythmic fast subthreshold depolarizations in thalamic relay cells of rats under urethane anaesthesia
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乌拉坦麻醉下大鼠丘脑中继细胞节律性快速阈下去极化的起源
DOI：
10.1016/0006-8993(92)91063-k
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发表时间：
1992
期刊：
影响因子：
2.9
通讯作者：
M. Deschenes
中科院分区：
文献类型：
--
作者：
D. Pinault;M. Deschenes
在乌拉坦麻醉下对大鼠丘脑背侧中继神经元进行细胞内记录。在127个腹后外侧核和腹外侧核的神经元中，有77个在静息状态下呈现高节律性的阈值下去极化模式，而在腹后内侧核和后侧核团中则没有。这些节律性去极化在腹后外侧细胞的平均频率为23.36±11.48赫兹(范围：6~60赫兹)，在腹侧中继细胞的频率较高(65.86±17.42赫兹，范围：17~95赫兹)。节律性的阈值下事件被认为是由规则地放电位于背柱和小脑深核的丘脑前传入所产生的兴奋性突触后电位。事实上，在腹后外侧核的细胞中，这些自发电位的波形类似于由体感刺激触发的突触电位。它们的幅度随膜超极化而增加，它们的节律性发生不受大内向电流注入的影响。此外，切断包膜后，它们仍然存在，但在损伤后柱核的腹后外侧细胞中不能再记录到它们。最后发现，小脑深核团内的丘脑前传入在与腹侧核记录到的节律性突触电位相同的频段内以节律性的方式自发放电。根据这些结果，我们认为乌拉坦麻醉下动物丘脑神经元的节律性阈值下除极不是固有产生的，而是丘脑前部的兴奋性突触后电位。这些突触电位的节律性表明，背柱和小脑深部核团的神经元能够有节奏地编码它们的输出。在已经发表的关于大脑快速振荡起源的结果的背景下，这一有趣的观察应该值得进一步关注，因为之前在非麻醉或轻度麻醉的动物中报道的视网膜神经节细胞也有类似的节律。
Intracellular recordings were performed in relay neurons of the dorsal thalamus in rats under urethane anaesthesia. In 77 out of 127 neurons of the ventro-posterolateral and ventral lateral nuclei, but not in neurons of the ventro-posteromedial and posterior nuclei, a highly rhythmic pattern of subthreshold depolarization was present at rest. The average frequency of these rhythmic depolarizations in ventro-posterolateral cell was 23.36±11.48 Hz (range: 6–60 Hz); in ventral lateral relay cells higher frequencies were observed (65.86±17.42 Hz; range: 17–95 Hz). The rhythmic subthreshold events were identified as excitatory postsynaptic potentials generated by the regular firing of prethalamic afferents located in dorsal column and deep cerebellar nuclei. Indeed, in cells of the ventro-posterolateral nucleus these spontaneous potentials had a waveform similar to that synaptic potentials trigged by somatosensory stimulation. They increased in amplitude with membrane hyperpolarization and their rhythmic occurrence was not affected by the injection of large inward currents. Moreover, they persisted after capsular transection, but they could no more be recorded in ventro-posterolateral cells after lesion of dorsal column nuclei. Finally, it was found that prethalamic afferents within the deep cerebellar nuclei discharged spontaneously in a rhythmic manner within the same frequency band as that of the rhythmic synaptic potentials recorded in ventral lateral cells. On the basis of these results, it is concluded that the rhythmic subthreshold depolarization observed in thalamic neurons of animals under urethane anaesthesia are not generated intrinsically but that they represent excitatory postsynaptic potentials of prethalamic origin. The rhythmic nature of these synaptic potentials demonstrates that neurons of the dorsal column and deep cerebellar nuclei are capable of encoding rhythmically their output. In the context of results already published on the origin of fast oscillations in the brain, this intriguing observation should deserve further attention as much as a similar rhythm has previously been reported for retinal ganglion cells in non-anaesthetized or lightly anaesthetized animals.