Functional activity of the M2 and M4 receptor subtypes in the spinal cord studied with muscarinic acetylcholine receptor knockout mice
Functional activity of the M2 and M4 receptor subtypes in the spinal cord studied with muscarinic acetylcholine receptor knockout mice
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DOI：
10.1124/jpet.104.082537
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发表时间：
2005-05-01
影响因子：
3.5
通讯作者：
Pan, HL
中科院分区：
文献类型：
--
作者：
Chen, SR;Wess, J;Pan, HL
刺激脊髓毒蕈碱乙酰胆碱受体（mAChR）产生有效的镇痛作用。M-2和M-4 mAChR均与相似的G蛋白（G（i/o）家族）偶联，并在mAChR激动剂的镇痛作用中起关键作用。为了确定M2和M4亚型对脊髓中G（i/o）蛋白激活的相对贡献，我们在M-2和M-4亚型敲除（KO）小鼠中检测了受体介导的鸟苷5 '-O-（3-[S-35]硫代）三磷酸（[S-35]GTP γ S）结合。脊髓中的基础[S-35]GTP γ S结合在野生型对照、M-2和M-4单KO以及M-2/M-4双KO小鼠中相似。脊髓[S-35]GTP γ S结合刺激的毒蕈碱或oxotremorine-M之间没有显着差异三组野生型小鼠品系。在M2单KO和M-2/M-4双KO小鼠中，脊髓中激动剂刺激的[S-35]GTP γ S结合完全消除。此外，与野生型对照组相比，M4单基因敲除小鼠脊髓中激动剂刺激的[S-35]GTP γ S结合显著降低（接近15%）。另一方面，由μ-阿片激动剂刺激的脊髓[S-35]GTP γ S结合在野生型与M-2和M-4 KO小鼠之间没有显著差异。这项研究提供了补充的新证据，M-2是最主要的mAChR亚型耦合到G（i/o）蛋白在脊髓。此外，这些数据表明，一个小的，但功能显着的M-4受体的人口存在于小鼠脊髓。这些M-4受体的功能活性似乎需要M-2受体的存在。
Stimulation of spinal muscarinic acetylcholine receptors (mAChRs) produces potent analgesia. Both M-2 and M-4 mAChRs are coupled to similar G proteins (G(i/o) family) and play a critical role in the analgesic action of mAChR agonists. To determine the relative contribution of M 2 and M 4 subtypes to activation of G(i/o) proteins in the spinal cord, we examined the receptor-mediated guanosine 5'-O-(3-[S-35]thio)triphosphate ([S-35]GTP gamma S) binding in M-2 and M-4 subtype knockout (KO) mice. Basal [S-35]GTP gamma S binding in the spinal cord was similar in the wild-type controls, M-2 and M-4 single-KO, and M-2/M-4 double-KO mice. The spinal [S-35]GTP gamma S binding stimulated by either muscarine or oxotremorine-M was not significantly different among three groups of wild-type mouse strains. In M 2 single-KO and M-2/M-4 double-KO mice, the agonist-stimulated [S-35]GTP gamma S binding was completely abolished in the spinal cord. Furthermore, the agonist-stimulated [S-35]GTP gamma S binding in the spinal cord of M 4 single-KO mice was significantly reduced (similar to 15%), compared with that in wild-type controls. On the other hand, the spinal [S-35]GTP gamma S binding stimulated by a mu-opioid agonist was not significantly different between wildtype and M-2 and M-4 KO mice. This study provides complementary new evidence that M-2 is the most predominant mAChR subtype coupled to the G(i/o) proteins in the spinal cord. Furthermore, these data suggest that a small but functionally significant population of M-4 receptors exists in the mouse spinal cord. The functional activity of these M-4 receptors seems to require the presence of M-2 receptors.