Department of Integrative Medicine and Neurobiology, Institutes of Integrative Medicine, School of Basic Medical Sciences, Institutes of Brain Science, Brain Science Collaborative Innovation Center, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, 130 Dong'an Road, Xuhui District, Shanghai, China.
Department of Pain Management, Shandong Provincial Qianfoshan Hospital, the First Hospital Affiliated with Shandong First Medical University, Jinan, Shandong, China.
Acta Neuropathol Commun. 2020 Apr 7;8(1):44. doi: 10.1186/s40478-020-00922-9.
Trigeminal neuralgia (TN) is debilitating and is usually accompanied by mood disorders. The lateral habenula (LHb) is considered to be involved in the modulation of pain and mood disorders, and the present study aimed to determine if and how the LHb participates in the development of pain and anxiety in TN. To address this issue, a mouse model of partial transection of the infraorbital nerve (pT-ION) was established. pT-ION induced stable and long-lasting primary and secondary orofacial allodynia and anxiety-like behaviors that correlated with the increased excitability of LHb neurons. Adeno-associated virus (AAV)-mediated expression of hM4D(Gi) in glutamatergic neurons of the unilateral LHb followed by clozapine-N-oxide application relieved pT-ION-induced anxiety-like behaviors but not allodynia. Immunofluorescence validated the successful infection of AAV in the LHb, and microarray analysis showed changes in gene expression in the LHb of mice showing allodynia and anxiety-like behaviors after pT-ION. Among these differentially expressed genes was Tacr3, the downregulation of which was validated by RT-qPCR. Rescuing the downregulation of Tacr3 by AAV-mediated Tacr3 overexpression in the unilateral LHb significantly reversed pT-ION-induced anxiety-like behaviors but not allodynia. Whole-cell patch clamp recording showed that Tacr3 overexpression suppressed nerve injury-induced hyperexcitation of LHb neurons, and western blotting showed that the pT-ION-induced upregulation of p-CaMKII was reversed by AAV-mediated Tacr3 overexpression or chemicogenetic inhibition of glutamatergic neurons in the LHb. Moreover, not only anxiety-like behaviors, but also allodynia after pT-ION were significantly alleviated by chemicogenetic inhibition of bilateral LHb neurons or by bilateral Tacr3 overexpression in the LHb. In conclusion, Tacr3 in the LHb plays a protective role in treating trigeminal nerve injury-induced allodynia and anxiety-like behaviors by suppressing the hyperexcitability of LHb neurons. These findings provide a rationale for suppressing unilateral or bilateral LHb activity by targeting Tacr3 in treating the anxiety and pain associated with TN.
三叉神经痛（TN）是一种使人虚弱的疾病，通常伴有情绪障碍。外侧缰核（LHb）被认为参与了疼痛和情绪障碍的调节，本研究旨在确定 LHb 是否以及如何参与 TN 中疼痛和焦虑的发展。为了解决这个问题，建立了眶下神经部分横断（pT-ION）的小鼠模型。pT-ION 诱导稳定且持久的原发性和继发性口腔面部感觉异常和焦虑样行为，与 LHb 神经元兴奋性增加相关。腺相关病毒（AAV）介导的单侧 LHb 谷氨酸能神经元中 hM4D（Gi）的表达，随后应用氯氮平-N-氧化物，缓解了 pT-ION 诱导的焦虑样行为，但没有缓解感觉异常。免疫荧光验证了 AAV 在 LHb 中的成功感染，微阵列分析显示，pT-ION 后出现感觉异常和焦虑样行为的小鼠 LHb 中的基因表达发生变化。在这些差异表达的基因中，Tacr3 的表达下调，通过 RT-qPCR 进行了验证。通过 AAV 介导的 Tacr3 在单侧 LHb 中的过表达来挽救 Tacr3 的下调，显著逆转了 pT-ION 诱导的焦虑样行为，但没有缓解感觉异常。全细胞膜片钳记录显示，Tacr3 过表达抑制了神经损伤诱导的 LHb 神经元过度兴奋，Western blot 显示，AAV 介导的 Tacr3 过表达或 LHb 中谷氨酸能神经元的化学遗传抑制逆转了 pT-ION 诱导的 p-CaMKII 上调。此外，通过化学遗传抑制双侧 LHb 神经元或通过在 LHb 中双侧过表达 Tacr3，不仅 pT-ION 后的焦虑样行为，而且感觉异常也得到了显著缓解。总之，LHb 中的 Tacr3 通过抑制 LHb 神经元的过度兴奋，在治疗三叉神经损伤诱导的感觉异常和焦虑样行为中发挥保护作用。这些发现为通过靶向 Tacr3 抑制单侧或双侧 LHb 活性来治疗与 TN 相关的焦虑和疼痛提供了依据。
