Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan; Department of Dental Anesthesiology, School of Dental Medicine, Tsurumi University, Yokohama, Japan.
Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan; Department of Anesthesiology, Teikyo University School of Medicine, Tokyo, Japan.
Neuropharmacology. 2022 Jun 1;210:109029. doi: 10.1016/j.neuropharm.2022.109029. Epub 2022 Mar 16.
The "nociplastic pain," a recently proposed novel mechanistic pain descriptor, is defined as pain occurring through altered nociception without nociceptor activation and nerve injury. Nociplastic pain is often characterized by widespread pain sensitization (WSP) in multiple body regions (Fitzcharles et al., 2021). As many patients with primary chronic pain would have nociplastic backgrounds, developing appropriate methods to evaluate drug effects against nociplastic pain in animal model is in great demand. Using two rat models with the WSP involving central amygdala (CeA) activation by orofacial inflammation or direct chemogenetic activation (Sugimoto et al., 2021), we examined whether widely used analgesics, acetaminophen (AcAph), pregabalin (PGB), and duloxetine (DLX) could attenuate the WSP. AcAph (100 or 200 mg/kg, i.p.) significantly elevated 50%-paw withdrawal threshold (PWT), which had been lowered significantly by upper lip injection of formalin, or systemic injection of clozapine-N-oxide in the rats with excitatory designer receptors (hM3Dq) expressed in the right CeA. This effect lasted for > ∼4 h. PGB (30 mg/kg, i.p.) also significantly counteracted the lowered PWT in rats with orofacial formalin injection for >∼6 h. DLX was ineffective on the WSP. Based on these results, we propose that these preclinical models could be used to evaluate drug effects for primary chronic pain. We conclude that the widely used pain killers, AcAph and PGB, also relieve nociplastic widespread sensitization in the absence of ongoing nociceptor activation and nerve injury.
“病理性疼痛”是一种新提出的机制性疼痛描述,定义为在没有伤害感受器激活和神经损伤的情况下,通过改变伤害感受而产生的疼痛。病理性疼痛通常表现为广泛的痛觉过敏(WSP),涉及多个身体区域(Fitzcharles 等人,2021 年)。由于许多慢性原发性疼痛患者存在病理性疼痛背景,因此非常需要开发适当的方法来评估动物模型中针对病理性疼痛的药物疗效。我们使用了两种涉及中央杏仁核(CeA)激活的大鼠模型,一种是由口腔炎症引起的,另一种是直接化学遗传激活的(Sugimoto 等人,2021 年),我们研究了广泛使用的镇痛剂对乙酰氨基酚(AcAph)、普瑞巴林(PGB)和度洛西汀(DLX)是否能减轻 WSP。AcAph(100 或 200mg/kg,ip)显著提高了 50%的足底退缩阈值(PWT),而这种阈值在大鼠的上唇注射福尔马林或系统注射 Clozapine-N-oxide 后显著降低,这些大鼠的右侧 CeA 中表达了兴奋性设计受体(hM3Dq)。这种效应持续了 >∼4 小时。PGB(30mg/kg,ip)也显著对抗了口腔福尔马林注射大鼠的 PWT 降低,持续时间超过 >∼6 小时。DLX 对 WSP 无效。基于这些结果,我们提出这些临床前模型可用于评估治疗原发性慢性疼痛的药物疗效。我们的结论是,广泛使用的止痛药 AcAph 和 PGB 也能缓解没有持续伤害感受器激活和神经损伤的病理性广泛敏感化。
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