Bordia Tanuja, McGregor Matthew, Papke Roger L, Decker Michael W, McIntosh J Michael, Quik Maryka
Center for Health Sciences, SRI International, 333 Ravenswood Ave., Menlo Park, CA 94025, USA.
Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL 3261, USA.
Exp Neurol. 2015 Jan;263:277-84. doi: 10.1016/j.expneurol.2014.09.015. Epub 2014 Sep 28.
The finding that smoking is inversely correlated with Parkinson's disease and that nicotine attenuates nigrostriatal damage in Parkinsonian animals supports the idea that nicotine may be neuroprotective. Nicotine is thought to exert this effect by acting at nicotinic receptors (nAChRs), including the α7 subtype. The objective of this study was twofold: first, to test the protective potential of ABT-107, an agonist with high selectivity for α7 nAChRs; and second, to investigate its cellular mechanism of action. Rats were implanted with minipumps containing ABT-107 (0.25mg/kg/d). In addition, we tested the effect of nicotine (1mg/kg/d) as a positive control, and also DMXB (2mg/kg/d) which acts primarily with α7 but also α4β2* nAChRs. Two weeks after minipump placement, the rats were lesioned by unilateral administration of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle. Lesioning alone decreased contralateral forelimb use and adjusted stepping, two measures of Parkinsonism. ABT-107 and nicotine treatment significantly improved these behaviors at all weeks tested, with variable improvement with DMXB. We next investigated the cellular mechanism involved. The striatal dopamine transporter (DAT), a marker of dopaminergic integrity, was reduced ~70% with lesioning. ABT-107 or nicotine treatment significantly increased DAT levels in lesioned striatum; these drugs did not alter DAT levels in intact striatum. ABT-107 and nicotine also significantly improved basal dopamine release from lesioned striatum, as well as nicotine-stimulated dopamine release mediated via α4β2* and α6β2* nAChRs. These data suggest that α7 nAChR agonists may improve motor behaviors associated with nigrostriatal damage by enhancing striatal dopaminergic function.
吸烟与帕金森病呈负相关,且尼古丁可减轻帕金森病动物的黑质纹状体损伤,这一发现支持了尼古丁可能具有神经保护作用的观点。人们认为尼古丁通过作用于烟碱型受体(nAChRs)发挥这种效应,包括α7亚型。本研究的目的有两个:第一,测试对α7 nAChRs具有高选择性的激动剂ABT - 107的保护潜力;第二,研究其细胞作用机制。给大鼠植入含有ABT - 107(0.25mg/kg/天)的微型泵。此外,我们测试了尼古丁(1mg/kg/天)作为阳性对照的效果,以及主要作用于α7但也作用于α4β2* nAChRs的DMXB(2mg/kg/天)的效果。在植入微型泵两周后,通过向内侧前脑束单侧注射6 - 羟基多巴胺(6 - OHDA)使大鼠产生损伤。单独损伤会降低对侧前肢的使用和调整步幅,这是帕金森病的两项指标。在所有测试周,ABT - 107和尼古丁治疗均显著改善了这些行为,DMXB的改善情况则有所不同。接下来我们研究了其中涉及的细胞机制。纹状体多巴胺转运体(DAT)是多巴胺能完整性的标志物,损伤使其减少了约70%。ABT - 107或尼古丁治疗显著提高了损伤纹状体中的DAT水平;这些药物并未改变完整纹状体中的DAT水平。ABT - 107和尼古丁还显著改善了损伤纹状体的基础多巴胺释放,以及通过α4β2和α6β2 nAChRs介导的尼古丁刺激的多巴胺释放。这些数据表明,α7 nAChR激动剂可能通过增强纹状体多巴胺能功能来改善与黑质纹状体损伤相关的运动行为。