MrgC受体激活翻转慢性应用吗啡诱发的谷氨酸转运体和nNOS改变

MrgC receptor activation reverses chronic morphine-evoked alterations of glutamate transporters and nNOS in rats

本研究旨在探讨激活MrgC受体(Mas-related gene C receptors)调制吗啡耐受的细胞学机制。对大鼠连续6天鞘内注射10μL生理盐水、吗啡(20μg)、吗啡+牛肾上腺髓质8-22(bovine adrenal medulla 8-22,BAM8-22,1 nmol,隔天注射)或(Tyr6)-2-MSH-6-12(MSH,5 nmol,隔天注射);用Western blot、免疫组织化学和实时荧光定量PCR的方法检测脊髓和背根神经节(dorsal root ganglion,DRG)中与吗啡耐受相关分子的表达。结果显示:鞘内给予选择性MrgC受体激动剂BAM8-22或MSH,能抑制慢性应用吗啡所诱发的脊髓背角和/或DRG中谷氨酸转运体(GLAST、GLT-1、EAAC1)的减少和神经元型一氧化氮合酶(neuronal nitric oxide synthase,nNOS)的增加。此外,检测到MrgC受体样免疫活性表达于脊髓背角浅层;慢性应用吗啡使脊髓背角MrgC受体样免疫活性和DRG中MrgC受体mRNA水平都增加。这些结果提示,MrgC受体通过抑制慢性应用吗啡所诱发的脊髓和DRG中的痛介质增加,而抑制吗啡耐受。

This study was aimed to investigate the mechanisms underlying the modulation effect ofMas-related gene （Mrg） C recep- tors （MrgC） on morphine tolerance. Saline, morphine （20 ~tg）, morphine plus bovine adrenal medulla 8-22 （BAM8-22, 1 nmol） or （Tyr6）-2-MSH-6-12 （MSH, 5 nmol） were administered intrathecally in rats for 6 days. Pain-related molecules in the spinal cord and dorsal root ganglion （DRG） were examined using Western blot, immunocytochemistry and RT-PCR techniques. The results showed that intrathecal administration of the selective MrgC receptor agonists （BAM8-22 or MSH） remarkably attenuated or abolished chronic morphine-evoked reduction in glutamate transporters （GLAST, GLT-1 and EAAC1） in the spinal cord and increase in neuronal nitric oxide synthase （nNOS） in the spinal cord as well as DRG. In addition, MrgC receptor-like immunoreactivity （IR） was detected in superficial laminae of the spinal cord. Chronic morphine induced significant increases in MrgC receptor-IR in the spinal cord and MrgC receptor mRNA levels in DRG. These results suggest that the modulation of pro-nocicepfive mediators in the spinal cord and DRG underlies the inhibition of morphine tolerance by MrgC receptor activation.