Extrasynaptic α₅‐subunit containing GABA_A (α₅‐GABA_A) receptors participate in chronic pain. Previously, we reported a sex difference in the action of α₅‐GABA_A receptors in dysfunctional pain. However, the underlying mechanisms remain unknown. The aim of this study was to examine this sexual dimorphism in neuropathic rodents and the mechanisms involved. Female and male Wistar rats or ICR mice were subjected to nerve injury followed by α₅‐GABA_A receptor inverse agonist intrathecal administration, L‐655,708. The drug produced an antiallodynic effect in nerve‐injured female rats and mice, and a lower effect in males. We hypothesized that changes in α₅‐GABA_A receptor, probably influenced by hormonal and epigenetic status, might underlie this sex difference. Thus, we performed qPCR and western blot. Nerve injury increased α₅‐GABA_A mRNA and protein in female dorsal root ganglia (DRG) and decreased them in DRG and spinal cord of males. To investigate the hormonal influence over α₅‐GABA_A receptor actions, we performed nerve injury to ovariectomized rats and reconstituted them with 17β‐estradiol (E2). Ovariectomy abrogated L‐655,708 antiallodynic effect and E2 restored it. Ovariectomy decreased α₅‐GABA_A receptor and estrogen receptor α protein in DRG of neuropathic female rats, while E2 enhanced them. Since DNA methylation might contribute to α₅‐GABA_A receptor down‐regulation in males, we examined CpG island DNA methylation of α₅‐GABA_A receptor coding gene through pyrosequencing. Nerve injury increased methylation in male, but not female rats. Pharmacological inhibition of DNA methyltransferases increased α₅‐GABA_A receptor and enabled L‐655,708 antinociceptive effect in male rats. These results suggest that α₅‐GABA_A receptor is a suitable target to treat chronic pain in females.

中文翻译：

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脊髓α5-GABAA受体的性别依赖性伤害感受作用及其在神经性啮齿动物中的表观遗传调控

突触外α ₅亚基含有GABA_甲（α ₅ -GABA_甲）受体参与慢性疼痛。此前，我们曾报道α的作用性别差异₅ -GABA_一个受体功能失调性疼痛。但是，基本机制仍然未知。这项研究的目的是检查神经性啮齿动物的这种性二态性及其所涉及的机制。雌性和雄性Wistar大鼠或ICR小鼠进行神经损伤，随后α ₅ -GABA_甲鞘内注射受体反向激动剂，L-655,708。该药物在神经损伤的雌性大鼠和小鼠中产生了抗痛觉过敏作用，而在雄性中则产生了较低的镇痛作用。我们假设在α的改变₅ -GABA_一个受体，可能是由激素和表观遗传状态的影响，可能这背后的性别差异。因此，我们进行了qPCR和蛋白质印迹。神经损伤增加α ₅ -GABA_甲mRNA和蛋白在雌性背根神经节（DRG），并将它们在DRG和男性的脊髓降低。探讨了α荷尔蒙的影响，₅ -GABA_一受体的作用，我们对去卵巢的大鼠进行了神经损伤，并用17β-雌二醇（E2）对其进行了重建。卵巢切除术废除了L‐655,708的抗痛觉过敏作用，E2恢复了它。卵巢切除降低α ₅ -GABA_甲在神经性雌性大鼠DRG受体和雌激素受体α蛋白，而E2增强它们。由于DNA甲基化可能有助于α ₅ -GABA_一个受体下调男性，我们研究了α的CpG岛甲基化DNA ₅ -GABA_一个受体编码基因通过焦磷酸测序。神经损伤会增加雄性大鼠的甲基化程度，但不会增加雌性大鼠的甲基化程度。DNA甲基转移酶的药理学抑制增加α ₅ -GABA_甲雌性大鼠体内的L-655708受体具有抗L -655,708的镇痛作用。这些结果表明，α ₅ -GABA_甲受体是合适的靶在女性治疗慢性疼痛。