Biotherapy Human Resources Center, College of Veterinary Medicine, Chonnam National University, Gwangju, South Korea.
Anesth Analg. 2010 Feb 1;110(2):622-9. doi: 10.1213/ANE.0b013e3181c8afc1. Epub 2009 Dec 10.
A previous study from our laboratories showed that a significant reduction in spinal N-methyl-D-aspartate (NMDA) receptor NR1 subunit phosphorylation (pNR1) is associated with the antiallodynic effect produced by intrathecal (IT) injection of the alpha-2 adrenoceptor agonist, clonidine, in neuropathic rats. In this study, we determined whether the spontaneous pain and increased pNR1 expression induced by NMDA injection are reduced by IT injection of either clonidine or the mu-opioid receptor agonist, [D-Ala2, NMe-Phe4, Gly-ol5]-enkephalin (DAMGO).
We examined the effect of clonidine (20 microg/rat) or DAMGO (1 microg/rat) injection on IT NMDA-induced spontaneous nociceptive behavior and pNR1 expression in the spinal dorsal horn. We also determined whether the effect of clonidine is mediated by alpha-2A or alpha-2C adrenoceptors. Finally, rat spinal cords were immunohistochemically processed for double staining of pNR1 and alpha-2A or alpha-2C adrenoceptors or mu-opioid receptors.
The NMDA-induced increase in both pNR1 expression and nociceptive behavior was significantly reduced by IT clonidine but not DAMGO. This analgesic effect of clonidine was blocked by administration of either an alpha-2A (BRL44408, 30 microg/rat) or an alpha-2C (JP-1302, 50 microg/rat) adrenoceptor antagonist. In addition, immunocytochemistry revealed that spinal pNR1 immunoreactive cells co-contain alpha-2A and alpha-2C adrenoceptors.
These results demonstrate that the IT NMDA-induced increase in pNR1 expression and nociceptive behavior is significantly reduced by activation of alpha-2 adrenoceptors, but not mu-opioid receptors, in the spinal cord dorsal horn. Furthermore, these findings suggest that the modulation of spinal NR1 phosphorylation is linked to the effect of IT clonidine on postsynaptic neuronal activity.
我们实验室的一项先前研究表明，鞘内注射 α-2 肾上腺素能激动剂可乐定可显著降低脊髓 N-甲基-D-天冬氨酸（NMDA）受体 NR1 亚单位磷酸化（pNR1），从而产生抗痛觉过敏作用。在这项研究中，我们确定鞘内注射可乐定或 μ-阿片受体激动剂 [D-Ala2，NMe-Phe4，Gly-ol5]-脑啡肽（DAMGO）是否可以减轻 NMDA 注射引起的自发性疼痛和增加的 pNR1 表达。
我们研究了可乐定（20μg/只大鼠）或 DAMGO（1μg/只大鼠）鞘内注射对 NMDA 诱导的 IT 自发性痛觉行为和脊髓背角 pNR1 表达的影响。我们还确定了可乐定的作用是否通过 α-2A 或 α-2C 肾上腺素能受体介导。最后，通过对 pNR1 和 α-2A 或 α-2C 肾上腺素能受体或 μ-阿片受体的双重免疫组织化学处理，确定大鼠脊髓。
NMDA 诱导的 pNR1 表达和痛觉行为增加均显著减少由 IT 可乐定，但不是 DAMGO。可乐定的这种镇痛作用被 α-2A（BRL44408，30μg/只大鼠）或 α-2C（JP-1302，50μg/只大鼠）肾上腺素能受体拮抗剂阻断。此外，免疫细胞化学显示脊髓 pNR1 免疫反应细胞共含有 α-2A 和 α-2C 肾上腺素能受体。
这些结果表明，脊髓背角 α-2 肾上腺素能受体的激活可显著降低 IT NMDA 诱导的 pNR1 表达和痛觉行为的增加，但不影响 μ-阿片受体。此外，这些发现表明，脊髓 NR1 磷酸化的调节与 IT 可乐定对突触后神经元活动的影响有关。
