Proprioceptive thalamus receiving forelimb and neck muscle spindle inputs via the external cuneate nucleus in the rat
Proprioceptive thalamus receiving forelimb and neck muscle spindle inputs via the external cuneate nucleus in the rat
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DOI：
10.1007/s00429-020-02118-2
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发表时间：
2020-08-03
影响因子：
3.1
通讯作者：
Yoshida, Atsushi
中科院分区：
文献类型：
--
作者：
Uemura, Yume;Haque, Tahsinul;Yoshida, Atsushi
来自身体肌肉的本体感受信号历来被认为投射到丘脑腹侧基底复合体的喙背壳[腹后外侧核（VPL）和腹后内侧核（VPM）]。然而，我们最近发现，本体感觉从大鼠下颌闭合肌梭（JCMSs）是通过三叉神经上核的尾腹内侧边缘的VPM，但不向rostrodoral壳的VPM。因此，来自其他身体肌肉的本体感受也可能投射到VPL的嘴背壳以外的丘脑区域。因此，我们研究了丘脑投射从大鼠外侧楔束核（ECu），接受本体输入前肢和颈部肌肉。将顺行示踪剂注入ECu后，轴突终末在VPL的腹内侧部（VPLvm）被对侧标记，但不在VPL的喙背壳中。将示踪剂顺行注入楔束核（Cu）后，对侧VPL（包括VPLvm）内的轴突终末被广泛标记。在VPLvm中，我们电生理学证实了对ECu或正中神经的电刺激以及对前肢/颈部肌肉或手腕屈曲的压力的本体感受输入。在VPLvm逆行注射示踪剂后，在ECu和Cu中对侧标记神经元。逆行示踪剂注射到VPL后，没有这样的本体感受输入记录，没有ECu神经元被标记。这些研究结果表明，本体感觉从前肢/颈部肌梭和JCMSs是somatotopically传输到ventrobasal丘脑复合体的ventromedial地板，但不是它的rostrodorthoral壳。
Proprioceptive signals from body muscles have historically been considered to project to the rostrodorsal shell of the ventrobasal thalamic complex [the ventral posterolateral nucleus (VPL) and ventral posteromedial nucleus (VPM)]. However, we have recently found that proprioception from rat jaw-closing muscle spindles (JCMSs) is conveyed via the supratrigeminal nucleus to the caudo-ventromedial edge of the VPM, but not to the rostrodorsal shell of the VPM. Therefore, proprioception from other body muscles may also project to thalamic regions other than the rostrodorsal shell of the VPL. We thus examined the thalamic projection from the rat external cuneate nucleus (ECu), which receives proprioceptive inputs from forelimb and neck muscles. After injection of anterograde tracer into the ECu, axon terminals were contralaterally labeled in the ventromedial part (VPLvm) of the VPL, but not in the rostrodorsal shell of the VPL. After anterograde tracer injection into the cuneate nucleus (Cu), axon terminals were widely labeled in the contralateral VPL including the VPLvm. In the VPLvm, we electrophysiologically confirmed the proprioceptive inputs responsive to electrical stimulation of the ECu or median nerve and to the pressure of forelimb/neck muscles or wrist flexion. After retrograde tracer injection into the VPLvm, neurons were contralaterally labeled in the ECu and Cu. After retrograde tracer injection into the VPL where no such proprioceptive inputs were recorded, no ECu neurons were labeled. These findings indicate that proprioception from forelimb/neck muscle spindles and JCMSs is somatotopically transmitted to the ventromedial floor of the ventrobasal thalamic complex, but not to its rostrodorsal shell.