Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China.
Emergency Department, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, China.
Neural Plast. 2020 Sep 22;2020:8876230. doi: 10.1155/2020/8876230. eCollection 2020.
Visceral hypersensitivity is a common occurrence of gastrointestinal diseases such as irritable bowel syndrome (IBS), wherein early-life stress (ELS) may have a high predisposition to the development of visceral hypersensitivity in adulthood, with the specific underlying mechanism still elusive. Herein, we assessed the potential effect of small-conductance calcium-activated potassium channel subtype 2 (SK2) in the spinal dorsal horn (DH) on the pathogenesis of visceral hypersensitivity induced by maternal separation (MS) in mice.
Neonatal mice were subjected to the MS paradigm, an established ELS model. In adulthood, the visceral pain threshold and the abdominal withdrawal reflex (AWR) were measured with an inflatable balloon. The elevated plus maze, open field test, sucrose preference test, and forced swim test were employed to evaluate the anxiety- and depression-like behaviors. The expression levels of SK2 in the spinal DH were determined by immunofluorescence and western blotting. The mRNA of SK2 and membrane palmitoylated protein 2 (MPP2) were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Electrophysiology was applied to evaluate the neuronal firing rates and SK2 channel-mediated afterhyperpolarization current ( ). The interaction between MPP2 and SK2 was validated by coimmunoprecipitation.
In contrast to the naïve mice, ethological findings in MS mice revealed lowered visceral pain threshold, more evident anxiety- and depression-like behaviors, and downregulated expression of membrane SK2 protein and MPP2 protein. Moreover, electrophysiological results indicated increased neuronal firing rates and decreased in the spinal DH neurons. Nonetheless, intrathecal injection of the SK2 channel activator 1-ethyl-2-benzimidazolinone (1-EBIO) in MS mice could reverse the electrophysiological alterations and elevate the visceral pain threshold. In the naïve mice, administration of the SK2 channel blocker apamin abated and elevated spontaneous neuronal firing rates in the spinal DH neurons, reducing the visceral pain threshold. Finally, disruption of the MPP2 expression by small interfering RNA (siRNA) could amplify visceral hypersensitivity in naïve mice.
ELS-induced visceral pain and visceral hypersensitivity are associated with the underfunction of SK2 channels in the spinal DH.
内脏敏感性是胃肠道疾病（如肠易激综合征（IBS））的常见现象，其中早期生活压力（ELS）可能使成年人易患内脏敏感性，但其具体潜在机制仍难以捉摸。在此，我们评估了小电导钙激活钾通道亚型 2（SK2）在脊髓背角（DH）中的潜在作用对母体分离（MS）诱导的小鼠内脏敏感性发病机制的影响。
新生小鼠接受 MS 范式，这是一种已建立的 ELS 模型。在成年期，使用可充气气球测量内脏疼痛阈值和腹部退缩反射（AWR）。高架十字迷宫、旷场试验、蔗糖偏好试验和强迫游泳试验用于评估焦虑和抑郁样行为。通过免疫荧光和 Western blot 测定脊髓 DH 中 SK2 的表达水平。通过定量实时聚合酶链反应（qRT-PCR）测定 SK2 和膜棕榈酰化蛋白 2（MPP2）的 mRNA。电生理学用于评估神经元放电率和 SK2 通道介导的超极化后电流（ ）。通过共免疫沉淀验证 MPP2 和 SK2 之间的相互作用。
与未处理的小鼠相比，MS 小鼠的行为学发现内脏疼痛阈值降低，焦虑和抑郁样行为更明显，脊髓 DH 神经元中的膜 SK2 蛋白和 MPP2 蛋白表达下调。此外，电生理结果表明，脊髓 DH 神经元的神经元放电率增加， 减少。然而，鞘内注射 SK2 通道激活剂 1-乙基-2-苯并咪唑啉酮（1-EBIO）可逆转电生理改变并提高内脏疼痛阈值。在未处理的小鼠中，SK2 通道阻断剂 apamin 的给药减少了脊髓 DH 神经元中的 并增加了自发性神经元放电率，降低了内脏疼痛阈值。最后，小干扰 RNA（siRNA）破坏 MPP2 的表达可放大未处理的小鼠的内脏敏感性。
ELS 诱导的内脏疼痛和内脏敏感性与脊髓 DH 中 SK2 通道的功能障碍有关。
