Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China.
Department of Anatomy, Fujian Health College, Fuzhou 350101, Fujian Province, China.
World J Gastroenterol. 2019 Oct 28;25(40):6077-6093. doi: 10.3748/wjg.v25.i40.6077.
Central sensitization plays a pivotal role in the maintenance of chronic pain induced by chronic pancreatitis (CP). We hypothesized that the nucleus tractus solitarius (NTS), a primary central site that integrates pancreatic afferents apart from the thoracic spinal dorsal horn, plays a key role in the pathogenesis of visceral hypersensitivity in a rat model of CP.
To investigate the role of the NTS in the visceral hypersensitivity induced by chronic pancreatitis.
CP was induced by the intraductal injection of trinitrobenzene sulfonic acid (TNBS) in rats. Pancreatic hyperalgesia was assessed by referred somatic pain filament assay. Neural activation of the NTS was indicated by immunohistochemical staining for Fos. Basic synaptic transmission within the NTS was assessed by electrophysiological recordings. Expression of vesicular glutamate transporters (VGluTs), N-methyl-D-aspartate receptor subtype 2B (NR2B), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subtype 1 (GluR1) was analyzed by immunoblotting. Membrane insertion of NR2B and GluR1 was evaluated by electron microscopy. The regulatory role of the NTS in visceral hypersensitivity was detected pharmacological approach and chemogenetics in CP rats.
TNBS treatment significantly increased the number of Fos-expressing neurons within the caudal NTS. The excitatory synaptic transmission was substantially potentiated within the caudal NTS in CP rats (frequency: 5.87 ± 1.12 Hz in CP rats 2.55 ± 0.44 Hz in sham rats, < 0.01; amplitude: 19.60 ± 1.39 pA in CP rats 14.71 ± 1.07 pA in sham rats; < 0.01). CP rats showed upregulated expression of VGluT2, and increased phosphorylation and postsynaptic trafficking of NR2B and GluR1 within the caudal NTS. Blocking excitatory synaptic transmission the AMPAR antagonist CNQX and the NMDAR antagonist AP-5 microinjection reversed visceral hypersensitivity in CP rats (abdominal withdraw threshold: 7.00 ± 1.02 g in CNQX group, 8.00 ± 0.81 g in AP-5 group and 1.10 ± 0.27 g in saline group, < 0.001). Inhibiting the excitability of NTS neurons chemogenetics also significantly attenuated pancreatic hyperalgesia (abdominal withdraw threshold: 13.67 ± 2.55 g in Gi group, 2.00 ± 1.37 g in Gq group, and 2.36 ± 0.67 g in mCherry group, < 0.01).
Our findings suggest that enhanced excitatory transmission within the caudal NTS contributes to pancreatic pain and emphasize the NTS as a pivotal hub for the processing of pancreatic afferents, which provide novel insights into the central sensitization of painful CP.
中央敏化在慢性胰腺炎（CP）引起的慢性疼痛维持中起着关键作用。我们假设孤束核（NTS）作为除胸段脊髓背角之外整合胰腺传入的主要中枢部位，在 CP 大鼠模型内脏超敏反应的发病机制中起关键作用。
研究 NTS 在慢性胰腺炎引起的内脏超敏反应中的作用。
通过三硝基苯磺酸（TNBS）在大鼠的胰管内注射诱导 CP。通过牵涉性躯体疼痛纤维测定法评估胰腺痛觉过敏。通过免疫组化染色 Fos 来指示 NTS 的神经激活。通过电生理记录评估 NTS 内基本的突触传递。通过免疫印迹分析囊泡谷氨酸转运体（VGluTs）、N-甲基-D-天冬氨酸受体 2B 亚型（NR2B）和 α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体 1 亚型（GluR1）的表达。通过电子显微镜评估 NR2B 和 GluR1 的膜插入。通过药理学方法和 CP 大鼠的化学遗传学检测 NTS 在内脏超敏反应中的调节作用。
TNBS 处理显著增加了 CP 大鼠尾侧 NTS 中表达 Fos 的神经元数量。CP 大鼠的兴奋性突触传递明显增强（频率：CP 大鼠 5.87 ± 1.12 Hz 与 sham 大鼠 2.55 ± 0.44 Hz，<0.01；幅度：CP 大鼠 19.60 ± 1.39 pA 与 sham 大鼠 14.71 ± 1.07 pA，<0.01）。CP 大鼠尾侧 NTS 中 VGluT2 表达上调，NR2B 和 GluR1 的磷酸化和突触后转运增加。用 AMPAR 拮抗剂 CNQX 和 NMDAR 拮抗剂 AP-5 微注射阻断兴奋性突触传递，逆转 CP 大鼠的内脏超敏反应（腹部退缩阈值：CNQX 组 7.00 ± 1.02 g，AP-5 组 8.00 ± 0.81 g，生理盐水组 1.10 ± 0.27 g，<0.001）。用化学遗传学抑制 NTS 神经元的兴奋性也显著减轻胰腺痛觉过敏（腹部退缩阈值：Gi 组 13.67 ± 2.55 g，Gq 组 2.00 ± 1.37 g，mCherry 组 2.36 ± 0.67 g，<0.01）。
我们的研究结果表明，尾侧 NTS 内的兴奋性传递增强导致胰腺疼痛，并强调 NTS 是胰腺传入的处理的关键枢纽，为疼痛性 CP 的中枢敏化提供了新的见解。
