Tata A M, Tripiciano A, Filippini A, Biagioni S, Augusti-Tocco G
Dipartimento di Biologia Cellulare e dello Sviluppo, Università 'La Sapienza', P. le Aldo Moro 5, 00185, Rome, Italy.
Brain Res. 2000 Jun 2;866(1-2):65-72. doi: 10.1016/s0006-8993(00)02225-3.
In the present work we have studied the variation of intracellular calcium levels induced by muscarinic agonists in chick dorsal root ganglia neurons. Muscarinic agonists such as muscarine and oxotremorine cause an increase of intracellular calcium levels in fura-2AM-loaded DRG neurons of E18 chick embryos. This increase was abolished following treatment with 1 microM atropine but not by 1 microM mecamylamine, indicating that the observed intracellular calcium increase, was dependent on muscarinic receptor activation. Stimulation in absence of external calcium or pre-incubation of the DRG cultures with thapsigargin or Mn(2+) demonstrated that Ca(2+) increase is mainly due to its release from intracellular stores. The use of selective antagonists of muscarinic receptor subtypes also indicated that M(1) and to a lesser extent M(3) receptor subtypes are responsible for the observed intracellular calcium mobilization. Finally pre-treatment of DRG cultures with pertussis toxin showed that the variation of Ca(2+) levels was dependent on PTX-insensitive G-protein. Moreover muscarinic agonists induce in DRG also the increase of IPs level, suggesting that the variations of intracellular calcium levels may be due at least in part to the activation of the phosphoinositide transduction pathway. In conclusion the reported observations demonstrate the activity of muscarinic receptors in sensory neurons, suggesting a functional role for acetylcholine in sensory transduction.
在本研究中，我们研究了毒蕈碱激动剂诱导鸡背根神经节神经元细胞内钙水平的变化。毒蕈碱激动剂如毒蕈碱和氧化震颤素可使E18鸡胚的fura-2AM加载的背根神经节（DRG）神经元细胞内钙水平升高。在用1 microM阿托品处理后，这种升高被消除，但1 microM美加明处理则无此效果，这表明观察到的细胞内钙升高依赖于毒蕈碱受体激活。在无细胞外钙的情况下进行刺激，或用毒胡萝卜素或Mn(2+)对DRG培养物进行预孵育，结果表明[Ca(2+)]i升高主要是由于其从细胞内储存库释放。使用毒蕈碱受体亚型的选择性拮抗剂也表明，M(1)受体亚型以及程度较轻的M(3)受体亚型是观察到的细胞内钙动员的原因。最后，用百日咳毒素对DRG培养物进行预处理表明，[Ca(2+)]i水平的变化依赖于对百日咳毒素不敏感的G蛋白。此外，毒蕈碱激动剂在DRG中还诱导肌醇磷酸水平升高，这表明细胞内钙水平的变化可能至少部分归因于磷酸肌醇转导途径的激活。总之，所报道的观察结果证明了毒蕈碱受体在感觉神经元中的活性，提示乙酰胆碱在感觉转导中具有功能作用。
