Expression and Agonist‐Induced Down‐Regulation of mRNAs of m2‐ and m3‐Muscarinic Acetylcholine Receptors in Cultured Cerebellar Granule Cells
Expression and Agonist‐Induced Down‐Regulation of mRNAs of m2‐ and m3‐Muscarinic Acetylcholine Receptors in Cultured Cerebellar Granule Cells
复制标题
培养的小脑颗粒细胞中 m2 和 m3 毒蕈碱乙酰胆碱受体 mRNA 的表达和激动剂诱导的下调
作者：
F. Fukamauchi;C. Hough;D. Chuang
摘要：采用Northern blot杂交技术研究了培养的小脑颗粒细胞毒蕈碱乙酰胆碱受体（mAChR） mRNA的表达调控。在这些细胞中检测到m2‐和m3‐machr的mRNA种类，但未检测到ml‐和m4‐machr。m2‐和m3‐machr mrna的表达在培养第10天达到最大值，但其表达模式不同。用100 μM苯酚培养8天后的小脑颗粒细胞导致两种mAChR亚型mRNA种类的差异下调。麝香碱受体拮抗剂阿托品（1 μM）和匹伦齐平（10 μM）在8 h时可阻止碳巴酚诱导的m3‐mAChR mRNA下调。然而，单独暴露于阿托品或匹伦齐平8 h后，m3‐mAChR mRNA显著上调。因此，m2‐和m3‐mAChR亚型的mRNA种类在培养物中表达不同，并在激动剂刺激下下调。这些mRNA物种的缺失可能在脱敏后发生的mAChR结合位点的下调中起作用。
Abstract: The regulation and expression of muscarinic acetylcholine receptor (mAChR) mRNA was studied in cultured cerebellar granule cells using Northern blot hybridization. mRNA species for m2‐ and m3‐mAChRs but not ml‐ and m4‐mAChRs were detected in these cells. The expression of mRNAs of both m2‐ and m3‐mAChRs reached a maximum on the tenth day in culture but their expression patterns differed. Treatment of cerebellar granule cells after 8 days in culture with 100 μM carbachol led to differential down‐regulation of the mRNA species of both mAChR subtypes present. Muscarinic receptor antagonists, atropine (1 μM) and pirenzepine (10 μM), prevented carbachol‐induced m3‐mAChR mRNA down‐regulation observed at 8 h. However, exposure to either atropine or pirenzepine alone for 8 h led to a significant up‐regulation of m3‐mAChR mRNA. Thus, the mRNA species for both m2‐ and m3‐mAChR subtypes are differentially expressed in culture and down‐regulated by agonist stimulation. The loss of these mRNA species may play a role in the down‐regulation of mAChR binding sites that occurs after desensitization.