胍丁胺-I1咪唑啉受体对μ阿片受体下调的影响及可能机制

目的:观察胍丁胺通过激活I1咪唑啉受体(I1R)对阿片预处理引起的μ阿片受体(MOR)下调的影响及可能的分子基础。方法:以CHO-μ和CHO-μ/IRAS(imidazoline receptor antisera-selected protein)细胞作为研究对象,用3H]diprenorphine结合实验方法,确定胍丁胺-I1R作用系统对MOR下调的影响以及可能产生的分子基础。结果:在正常CHO-μ和CHO-μ/IRAS细胞中,DAMGO(D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin,1μmol·L-1)处理两细胞12h后均可出现MOR的下调,胍丁胺(1-100nmol·L-1)浓度依赖性地抑制CHO-μ/IRAS细胞中MOR的下调,而相同浓度胍丁胺在CHO-μ细胞中无此作用。胍丁胺这一作用能被I1R阻断剂依法克生(efaroxan,Efa)所阻断。DAMGO(1μmol·L-1)预处理两细胞30min后,MOR均发生内吞。胍丁胺(1nmol.L-1-1μmol·L-1)和DAMGO共同预处理两细胞30min,胍丁胺能浓度依赖性地抑制由DAMGO预处理引起的CHO-μ/IRAS细胞中MOR的内吞,而相同浓度胍丁胺对CHO-μ细胞中由DAMGO预处理引起的MOR的内吞无显著影响,且这一作用同样能被依法克生所阻断,提示胍丁胺通过激活I1R对DAMGO预处理引起的MOR内吞具有显著的抑制作用,这可能是胍丁胺-I1R作用系统抑制MOR下调的分子基础。结论:胍丁胺通过激活I1R抑制阿片激动剂诱导的MOR的内吞,进而进一步抑制MOR下调。

MODULATION OF AGMATINE ON DOWN-REGULATION OF MU-OPIOID RECEPTOR BY ACTIVATION OF I1 IMIDAZOLINE RECEPTOR AND ITS MOLECULAR MECHANISM

Objective:To investigate the effects of agmatine by activation I1 imidazoline receptor on DAMGO-induced down-regulation and internalization of μ opioid receptor(MOR).Methods:Two cell lines,Chinese hamster ovary cells expressing μ opioid receptor alone(CHO-μ)and co-expressing μ opioid receptor and imidazoline receptor antisera-selected protein(IRAS),a candidate for I1 imidazoline receptor,(CHO-μ/IRAS),were used.\3H\]diprenorphine binding assay was used to determine the effect on the down-regulation of μ opioid receptor by agmatine-I1 imidazoline receptor system and its molecular mechanism.Results:In normal CHO-μ and CHO-μ/IRAS cells,chronic treatment by DAMGO(\D-Ala2,N-Me-Phe4,Gly5-ol\]-enkephalin,1 μmol·L-1,12 h)decreased the expression of MOR.Agmatine(1-100 nmol·L-1)concentration dependently inhibited DAMGO-induced down-regulation of MOR in CHO-μ/IRAS cells,while this effect was not observed in CHO-μ cells.Efaroxan,an I1 imidazoline receptor-preferential antagonist,completely reversed the effect of agmatine in CHO-μ/IRAS cells.DAMGO(1 μmol·L-1)treatment for 30 min induced internalization of MOR in both cells.Agmatine(1 nmol·L-1-1 μmol·L-1)concentration dependently inhibited DAMGO-induced internalization of MOR in CHO-μ/IRAS cells,while this effect was not observed in CHO-μ cells.Efaroxan completely reversed the effect of agmatine in CHO-μ/IRAS cells.This result suggested that agmatine acting on I1R inhibits internalization of MOR,and then inhibits its down-regulation.Conclusion:Agmatine acting on I1R could inhibit internalization of MOR,and then inhibit its down-regulation.