Talka Reeta, Salminen Outi, Tuominen Raimo K
Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland.
Basic Clin Pharmacol Toxicol. 2015 Apr;116(4):321-8. doi: 10.1111/bcpt.12317. Epub 2014 Oct 7.
Nicotine-methadone interactions have been studied in human beings and in various experimental settings regarding addiction, reward and pain. Most methadone maintenance treatment patients are smokers, and methadone administration has been shown to increase cigarette smoking. Previous in vitro studies have shown that methadone is a non-competitive antagonist at rat α3β4 nicotinic acetylcholine receptors (nAChR) and an agonist at human α7 nAChRs. In this study, we used cell lines expressing human α4β2, α7 and α3* nAChRs to compare the interactions of methadone at the various human nAChRs under the same experimental conditions. A [(3) H]epibatidine displacement assay was used to determine whether methadone binds to the nicotinic receptors, and (86) Rb(+) efflux and changes in intracellular calcium [Ca(2+) ]i were used to assess changes in the functional activity of the receptors. Methadone displaced [(3) H]epibatidine from nicotinic agonist-binding sites in SH-EP1-hα7 and SH-SY5Y cells, but not in SH-EP1-hα4β2 cells. The Ki values for methadone were 6.3 μM in SH-EP1-hα7 cells and 19.4 μM and 1008 μM in SH-SY5Y cells. Methadone increased [Ca(2+) ]i in all cell lines in a concentration-dependent manner, and in SH-EP1-hα7 cells, the effect was more pronounced than the effect of nicotine treatment. In SH-EP1-hα4β2 cells, the effect of methadone was negligible compared to that of nicotine. Methadone pre-treatment abolished the nicotine-induced response in [Ca(2+) ]i in all cell lines expressing nAChRs. In SH-EP1-hα4β2 and SH-SY5Y cells, methadone had no effect on the (86) Rb(+) efflux, but it antagonized the nicotine-induced (86) Rb(+) ion efflux in a non-competitive manner. These results suggest that methadone is an agonist at human α7 nAChRs and a non-competitive antagonist at human α4β2 and α3* nAChRs. This study adds further support to the previous findings that opioids interact with nAChRs, which may underlie their frequent co-administration in human beings and might be of interest to the field of drug discovery.
尼古丁与美沙酮的相互作用已在人类及各种关于成瘾、奖赏和疼痛的实验环境中得到研究。大多数接受美沙酮维持治疗的患者是吸烟者，并且已表明服用美沙酮会增加吸烟量。先前的体外研究表明，美沙酮是大鼠α3β4烟碱型乙酰胆碱受体（nAChR）的非竞争性拮抗剂，也是人类α7 nAChR的激动剂。在本研究中，我们使用表达人类α4β2、α7和α3* nAChR的细胞系，在相同实验条件下比较美沙酮在各种人类nAChR上的相互作用。采用[³H]埃博霉素置换试验来确定美沙酮是否与烟碱型受体结合，并用⁸⁶Rb⁺外流和细胞内钙[Ca²⁺]i的变化来评估受体功能活性的变化。美沙酮能从SH-EP1-hα7和SH-SY5Y细胞中的烟碱型激动剂结合位点置换出[³H]埃博霉素，但在SH-EP1-hα4β2细胞中不能。美沙酮在SH-EP1-hα7细胞中的Ki值为6.3 μM，在SH-SY5Y细胞中为19.4 μM和1008 μM。美沙酮以浓度依赖性方式增加所有细胞系中的[Ca²⁺]i水平，并且在SH-EP1-hα7细胞中，其作用比尼古丁处理的作用更明显。在SH-EP1-hα4β2细胞中，与尼古丁相比，美沙酮的作用可忽略不计。美沙酮预处理消除了所有表达nAChR的细胞系中尼古丁诱导的[Ca²⁺]i反应。在SH-EP1-hα4β2和SH-SY5Y细胞中，美沙酮对⁸⁶Rb⁺外流无影响，但它以非竞争性方式拮抗尼古丁诱导的⁸⁶Rb⁺离子外流。这些结果表明，美沙酮是人类α7 nAChR的激动剂，是人类α4β2和α3* nAChR的非竞争性拮抗剂。本研究进一步支持了先前的发现，即阿片类药物与nAChR相互作用，这可能是它们在人类中经常联合使用的基础，并且可能对药物发现领域具有重要意义。
