Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, Leioa, Spain Department of Neurosciences, School of Pharmacy, University of the Basque Country, Vitoria-Gasteiz, Spain Department of Surgery, Radiology and Physical Medicine, University of the Basque Country, Bilbao, Spain Department of Preventive Medicine and Public Health, School of Medicine and Dentistry, University of the Basque Country, Leioa, Spain.
Pain. 2012 Jul;153(7):1418-1425. doi: 10.1016/j.pain.2012.03.017. Epub 2012 Apr 19.
Opioid analgesia is compromised by intracellular mediators such as protein kinase C (PKC). The phosphatidylinositol hydrolysis-coupled serotonin receptor 5-HT2 is ideally suited to promote PKC activation. We test the hypothesis that 5-HT2A and 5-HT2B receptors, which have been previously shown to become pro-excitatory after spinal nerve ligation (SNL), can negatively influence the ability of opioids to depress spinal excitation evoked by noxious input. Spinal superfusion with (100 nM) mu-opioid receptor (MOR)-agonist DAMGO significantly depressed C fiber-evoked spinal field potentials. Simultaneous administration of subclinical 5-HT2AR antagonist 4F 4PP (100 nM) or 5-HT2BR antagonist SB 204741 (100 nM) significantly reduced the IC50 value for DAMGO in nerve-ligated rats (97.56 nM ± 1.51 and 1.20 nM ± 1.28 respectively, relative to 104 nM ± 1.08 at the baseline condition), but not in sham-operated rats. Both antagonists failed to alter depression induced by delta-opioid receptor (DOR)-agonist D-ala2-deltorphin II after SNL as well as in the sham condition. Western blot analysis of dorsal horn homogenates revealed bilateral upregulation of 5-HT2AR and 5-HT2BR protein band densities after SNL. As assessed from double immunofluorescence labeling for confocal laser scanning microscopy, scarce dorsal horn cell processes showed co-localization color overlay for 5-HT2AR/MOR, 5-HT2BR/MOR, 5-HT2AR/DOR, or 5-HT2BR/DOR in sham-operated rats. Intensity correlation-based analyses showed significant increases in 5-HT2AR/MOR and 5-HT2BR/MOR co-localizations after SNL. These results indicate that plasticity of spinal serotonergic neurotransmission can selectively reduce spinal MOR mechanisms via 5-HT2A and 5-HT2B receptors, including upregulation of the latter and increased expression in dorsal horn neurons containing MOR.
阿片类镇痛药的作用会受到细胞内介质的影响，如蛋白激酶 C（PKC）。与磷脂酰肌醇水解偶联的血清素受体 5-HT2 非常适合促进 PKC 的激活。我们验证了这样一个假设，即先前已显示在脊神经结扎（SNL）后变得兴奋性增加的 5-HT2A 和 5-HT2B 受体，可以负向影响阿片类药物抑制伤害性输入引起的脊髓兴奋的能力。脊髓灌流（100 nM）μ-阿片受体（MOR）激动剂 DAMGO 显著抑制 C 纤维诱发的脊髓场电位。同时给予亚临床剂量的 5-HT2AR 拮抗剂 4F-4PP（100 nM）或 5-HT2BR 拮抗剂 SB 204741（100 nM），显著降低了神经结扎大鼠中 DAMGO 的 IC50 值（分别为 97.56 nM ± 1.51 和 1.20 nM ± 1.28，相对于基线条件下的 104 nM ± 1.08），但在假手术大鼠中则没有。两种拮抗剂均未能改变 SNL 后δ-阿片受体（DOR）激动剂 D-ala2-deltorphin II 诱导的抑制作用，以及在假手术条件下的抑制作用。背角匀浆的 Western blot 分析显示，SNL 后双侧背角 5-HT2AR 和 5-HT2BR 蛋白条带密度上调。通过共聚焦激光扫描显微镜的双免疫荧光标记评估，在假手术大鼠中，很少有背角细胞突起显示 5-HT2AR/MOR、5-HT2BR/MOR、5-HT2AR/DOR 或 5-HT2BR/DOR 的共定位颜色叠加。基于强度相关的分析显示，SNL 后 5-HT2AR/MOR 和 5-HT2BR/MOR 的共定位显著增加。这些结果表明，脊髓 5-羟色胺能神经传递的可塑性可以通过 5-HT2A 和 5-HT2B 受体选择性地降低脊髓 MOR 机制，包括后者的上调和含有 MOR 的背角神经元中的表达增加。
