Evaluation of muscarinic agonist-induced analgesia in muscarinic acetylcholine receptor knockout mice
Evaluation of muscarinic agonist-induced analgesia in muscarinic acetylcholine receptor knockout mice
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DOI：
10.1124/mol.62.5.1084
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发表时间：
2002-11-01
影响因子：
3.6
通讯作者：
Wess, J
中科院分区：
文献类型：
--
作者：
Duttaroy, A;Gomeza, J;Wess, J
中枢活性毒蕈碱激动剂显示出显著的镇痛作用。鉴定介导这种活性的特定毒蕈碱乙酰胆碱受体（mAChR）亚型具有相当大的治疗意义。为了研究M-2和M-4受体亚型（两种G（i）/G（o）偶联的mAChR）在介导激动剂依赖性抗伤害感受中的作用，我们产生了一种M-2和M-4 mAChR缺陷的突变小鼠系[M-2/M-4双敲除（KO）小鼠]。在野生型小鼠中，中枢活性毒蕈碱激动剂的全身、鞘内或脑室内给药导致强烈的镇痛作用，表明毒蕈碱镇痛可由脊髓和脊髓上机制介导。引人注目的是，M-2/M-4双KO小鼠中毒蕈碱激动剂诱导的抗伤害感受完全消除，与应用途径无关。非选择性毒蕈碱激动剂oxotremorine在M-2受体单KO小鼠中显示出降低的镇痛效力，但在M-4受体单KO小鼠中保留了完全的镇痛活性。相比之下，化学衍生自地棘蛙素的两种新型毒蕈碱激动剂CMI-936和CMI-1145在M-2和M-4受体单KO小鼠中显示出降低的镇痛活性，与应用途径无关。放射性配体结合研究表明，与氧代震颤素相反，两种CMI化合物对M-4的亲和力比对M-2受体的亲和力高>6倍，这为所观察到的激动剂活性谱的差异提供了分子基础。这些数据提供了明确的证据表明，毒蕈碱镇痛是专门介导的M-2和M-4 mAChR的组合在脊髓和脊髓上的网站。这些发现应该是相当大的相关性受体亚型选择性毒蕈碱激动剂作为新型镇痛药物的发展。
Centrally active muscarinic agonists display pronounced analgesic effects. Identification of the specific muscarinic acetylcholine receptor (mAChR) subtype(s) mediating this activity is of considerable therapeutic interest. To examine the roles of the M-2 and M-4 receptor subtypes, the two G(i)/G(o)-coupled mAChRs, in mediating agonist-dependent antinociception, we generated a mutant mouse line deficient in both M-2 and M-4 mAChRs [M-2/M-4 double-knockout (KO) mice]. In wild-type mice, systemic, intrathecal, or intracerebroventricular administration of centrally active muscarinic agonists resulted in robust analgesic effects, indicating that muscarinic analgesia can be mediated by both spinal and supraspinal mechanisms. Strikingly, muscarinic agonist-induced antinociception was totally abolished in M-2/M-4 double-KO mice, independent of the route of application. The nonselective muscarinic agonist oxotremorine showed reduced analgesic potency in M-2 receptor single-KO mice, but retained full analgesic activity in M-4 receptor single-KO mice. In contrast, two novel muscarinic agonists chemically derived from epibatidine, CMI-936 and CMI-1145, displayed reduced analgesic activity in both M-2 and M-4 receptor single-KO mice, independent of the route of application. Radioligand binding studies indicated that the two CMI compounds, in contrast to oxotremorine, showed >6-fold higher affinity for M-4 than for M-2 receptors, providing a molecular basis for the observed differences in agonist activity profiles. These data provide unambiguous evidence that muscarinic analgesia is exclusively mediated by a combination of M-2 and M-4 mAChRs at both spinal and supraspinal sites. These findings should be of considerable relevance for the development of receptor subtype-selective muscarinic agonists as novel analgesic drugs.