Center for Health Sciences, SRI International, 333 Ravenswood Ave, Menlo Park, California 94025, USA.
Mol Pharmacol. 2010 Nov;78(5):971-80. doi: 10.1124/mol.110.067561. Epub 2010 Aug 23.
Nicotinic receptors (nAChRs) are important modulators of dopaminergic transmission in striatum, a region critical to Parkinson's disease. The nAChRs mainly involved are the α6β2* and α4β2* subtypes. Lesion studies show that the α6β2* receptor is decreased to a much greater extent with nigrostriatal damage than the α4β2* subtype raising the question whether this latter nAChR population is more important with increased nigrostriatal damage. To address this, we investigated the effect of varying nigrostriatal damage on α6β2* and α4β2* receptor-modulated dopamine signaling using cyclic voltammetry. This approach offers the advantage that changes in dopamine release can be observed under different neuronal firing conditions. Total single-pulse-evoked dopamine release decreased in direct proportion to declines in the dopamine transporter and dopamine uptake. We next used α-conotoxinMII and mecamylamine to understand the role of the α4β2* and α6β2* subtypes in release. Single-pulse-stimulated α6β2* and α4β2* receptor dopamine release decreased to a similar extent with increasing nigrostriatal damage, indicating that both subtypes contribute to the control of dopaminergic transmission with lesioning. Total burst-stimulated dopamine release also decreased proportionately with nigrostriatal damage. However, the role of the α4β2* and α6β2* nAChRs varied with different degrees of lesioning, suggesting that the two subtypes play a unique function with burst firing, with a somewhat more prominent and possibly more selective role for the α6β2* subtype. These data have important therapeutic implications because they suggest that drugs directed to both α4β2* and α6β2* nAChRs may be useful in the treatment of neurological disorders such as Parkinson's disease.
烟碱型乙酰胆碱受体(nAChRs)是纹状体多巴胺能传递的重要调节剂,纹状体是帕金森病的关键区域。主要涉及的 nAChRs 是 α6β2和 α4β2亚型。损伤研究表明,与 α4β2亚型相比,α6β2受体在黑质纹状体损伤时的减少程度要大得多,这就提出了一个问题,即在黑质纹状体损伤增加的情况下,后者的 nAChR 群体是否更为重要。为了解决这个问题,我们使用循环伏安法研究了黑质纹状体损伤程度对 α6β2和 α4β2受体调节的多巴胺信号的影响。这种方法的优点是可以在不同的神经元放电条件下观察到多巴胺释放的变化。单次脉冲诱发的多巴胺释放总量与多巴胺转运体和多巴胺摄取的下降成正比。接下来,我们使用 α-芋螺毒素 MII 和美金刚胺来了解 α4β2和 α6β2亚型在释放中的作用。随着黑质纹状体损伤的增加,单脉冲刺激的 α6β2和 α4β2受体多巴胺释放以相似的程度减少,表明这两种亚型都有助于控制损伤时的多巴胺传递。总爆发刺激的多巴胺释放也与黑质纹状体损伤成比例减少。然而,α4β2和 α6β2nAChRs 的作用随着损伤程度的不同而变化,这表明这两种亚型在爆发放电时具有独特的功能,其中 α6β2亚型的作用更为突出和可能更为特异。这些数据具有重要的治疗意义,因为它们表明,针对 α4β2和 α6β2*nAChRs 的药物可能对治疗帕金森病等神经退行性疾病有用。