Enkephalinergic Circuit Involved in Nociceptive Modulation in the Spinal Dorsal Horn
Enkephalinergic Circuit Involved in Nociceptive Modulation in the Spinal Dorsal Horn
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脑啡肽能回路参与脊髓背角的伤害性调节
DOI：
10.1016/j.neuroscience.2019.12.020
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发表时间：
2020-03-01
期刊：
影响因子：
3.3
通讯作者：
Li, Yun-Qing
中科院分区：
文献类型：
--
作者：
Bai, Yang;Li, Meng-Ying;Li, Yun-Qing
脑啡肽（ENK）与脊髓背角（SDH）内的疼痛调制有关。揭示ENK镇痛的机制需要对脊髓ENK能回路的解剖学和功能学的了解。在此，我们结合形态学和电生理学的研究，解开SDH内的局部ENK能电路。首先，在成年前脑啡肽原（PPE）-GFP基因敲入小鼠中观察脊髓ENK能神经元的分布模式。接下来，将逆行示踪剂四甲基罗丹明（TMR）或辣根过氧化物酶（HRP）注射到PPE-GFP小鼠的臂旁核（PBN）中。免疫荧光染色显示I-异凝集素B4（IB 4）标记的非肽能传入神经与TMR标记的I层内PBN投射神经元以及II层内PPE免疫反应（-ir）神经元紧密贴壁。一些TMR标记的神经元同时与IB 4和PPE免疫阳性终末密切相关。电子显微镜进一步证实了这些组件的突触连接。最后，将TMR注射到成年C57 BL/6小鼠的PBN中。全细胞膜片钳记录显示，δ阿片受体（DOR）激动剂[D-Pen（2，5）]-脑啡肽（DPDPE，1 μ M）可显著降低小兴奋性突触后电流（mEPSC）的频率，并降低TMR标记神经元的活动。结论：脊髓ENK能神经元接受来自初级传入神经的直接兴奋性输入，在伤害性刺激条件下，初级传入神经可能被直接募集释放ENK; ENK可通过突触前和突触后DORs抑制神经元向投射神经元的兴奋性传递。这些形态学和功能学证据可能解释了SDH内ENK发挥镇痛作用的机制。(C)2019年IBRO。由爱思唯尔有限公司出版。保留所有权利。
Enkephalin (ENK) has been implicated in pain modulation within the spinal dorsal horn (SDH). Revealing the mechanisms underlying ENK analgesia entails the anatomical and functional knowledge of spinal ENK-ergic circuits. Herein, we combined morphological and electrophysiological studies to unravel local ENK-ergic circuitry within the SDH. First, the distribution pattern of spinal ENK-ergic neurons was observed in adult preproenkephalin (PPE)-GFP knock-in mice. Next, the retrograde tracer tetramethylrhodamine (TMR) or horseradish peroxidase (HRP) was injected into the parabrachial nucleus (PBN) in PPE-GFP mice. Immunofluorescent staining showed I-isolectin B4 (IB4) labeled non-peptidergic afferents were in close apposition to TMR-labeled PBN-projecting neurons within lamina I as well as PPE-immunoreactivity (-ir) neurons within lamina II. Some TMR-labeled neurons were simultaneously in close association with both IB4 and PPE-ir terminals. Synaptic connections of these components were further confirmed by electron microscopy. Finally, TMR was injected into the PBN in adult C57BL/6 mice. Whole-cell patch recordings showed that delta-opioid receptor (DOR) agonist, [D-Pen(2,5)]-enkephalin (DPDPE, 1 mu M), significantly reduced the frequency of miniature excitatory postsynaptic current (mEPSC) and decreased the activity of TMR-labeled neurons. In conclusion, spinal ENKergic neurons receive direct excitatory inputs from primary afferents, which might be directly recruited to release ENK under the condition of noxious stimuli; ENK could inhibit the glutamatergic transmission towards projecting neurons via presynaptic and postsynaptic DORs. These morphological and functional evidence may explain the mechanisms underlying the analgesic effects exerted by ENK within the SDH. (C) 2019 IBRO. Published by Elsevier Ltd. All rights reserved.