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新生小鼠脊髓中间神经元的轴突通过背根发出。

Neonatal Mice Spinal Cord Interneurons Send Axons through the Dorsal Roots.

作者信息

Osuna-Carrasco Laura Paulina, Dueñas-Jiménez Sergio Horacio, Toro-Castillo Carmen, De la Torre Braniff, Aguilar-García Irene, Alpirez Jonatan, Castillo Luis, Dueñas-Jiménez Judith Marcela

机构信息

Department of Translational Bioengineering, CUCEI, University of Guadalajara, Guadalajara 44430, México.

Department of Neuroscience, CUCS, University of Guadalajara, Guadalajara 44340, México.

出版信息

Exp Neurobiol. 2022 Apr 30;31(2):89-96. doi: 10.5607/en21019.

Abstract

Spontaneous interneuron activity plays a critical role in developing neuronal networks. Discharges conducted antidromically along the dorsal root (DR) precede those from the ventral root's (VR) motoneurons. This work studied whether spinal interneurons project axons into the neonate's dorsal roots. Experiments were carried out in postnatal Swiss-Webster mice. We utilized a staining technique and found that interneurons in the spinal cord's dorsal horn send axons through the dorsal roots. In vitro electrophysiological recordings showed antidromic action potentials (dorsal root reflex; DRR) produced by depolarizing the primary afferent terminals. These reflexes appeared by stimulating the adjacent dorsal roots. We found that bicuculline reduced the DRR evoked by L5 dorsal root stimulation when recording from the L4 dorsal root. Simultaneously, the monosynaptic reflex (MR) in the L5 ventral root was not affected; nevertheless, a long-lasting after-discharge appeared. The addition of 2-amino-5 phosphonovaleric acid (AP5), an NMDA receptor antagonist, abolished the MR without changing the after-discharge. The absence of DRR and MR facilitated single action potentials in the dorsal and ventral roots that persisted even in low Ca2+ concentrations. The results suggest that firing interneurons could send their axons through the dorsal roots. These interneurons could activate motoneurons producing individual spikes recorded in the ventral roots. Identifying these interneurons and the persistence of their neuronal connectivity in adulthood remains to be established.

摘要

自发性中间神经元活动在发育中的神经网络中起着关键作用。沿背根(DR)逆向传导的放电先于腹根(VR)运动神经元的放电。这项研究探讨了脊髓中间神经元是否将轴突投射到新生小鼠的背根中。实验在出生后的瑞士韦伯斯特小鼠身上进行。我们利用一种染色技术发现,脊髓背角中的中间神经元通过背根发送轴突。体外电生理记录显示,通过使初级传入终末去极化产生的逆向动作电位(背根反射;DRR)。这些反射通过刺激相邻的背根出现。我们发现,当从L4背根记录时,荷包牡丹碱降低了L5背根刺激诱发的DRR。同时,L5腹根中的单突触反射(MR)不受影响;然而,出现了持久的后放电。添加NMDA受体拮抗剂2-氨基-5-磷酸戊酸(AP5)消除了MR,而不改变后放电。DRR和MR的缺失促进了背根和腹根中的单个动作电位,即使在低钙浓度下也持续存在。结果表明,放电的中间神经元可以通过背根发送其轴突。这些中间神经元可以激活运动神经元,产生在腹根中记录到的单个尖峰。确定这些中间神经元及其在成年期的神经元连接的持续性仍有待确定。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/6a70/9194636/34011fde9a8e/en-31-2-89-f1.jpg

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