Medical Research Council Anatomical Neuropharmacology Unit, Department of Pharmacology, University of Oxford, Oxford, UK.
Eur J Neurosci. 2011 Apr;33(7):1205-11. doi: 10.1111/j.1460-9568.2011.07594.x. Epub 2011 Mar 7.
Midbrain dopamine neurons signal rapid information about rewards and reward-related events. It has been suggested that this fast signal may, in fact, be conveyed by co-released glutamate. Evidence that dopamine neurons co-release glutamate comes largely from studies involving cultured neurons or tissue from young animals. Recently, however, it has been shown that this dual glutamatergic/dopaminergic phenotype declines with age, and can be induced by injury, suggesting that it is not a key feature of adult dopamine neurons. Here, we provide further support for this view by showing that dopaminergic axons and terminals in subregions of the adult striatum do not express vesicular glutamate transporters (VGluT1, VGluT2 or VGluT3). Striatal tissue from the adult rat was immunolabelled to reveal tyrosine hydroxylase (TH; biosynthetic enzyme of dopamine) and one of the three known VGluTs. Importantly, we compared the immunogold labelling for each of the VGluTs associated with TH-positive structures with background labelling at the electron microscopic level. In addition, we carried out a subregional analysis of the core and shell of the nucleus accumbens. We found that dopaminergic axons and terminals in the dorsolateral striatum and ventral striatum (nucleus accumbens core and shell) do not express VGluT1, VGluT2 or VGluT3. We conclude, therefore, that in the normal, adult rat striatum, dopaminergic axons do not co-release glutamate.
中脑多巴胺神经元快速传递关于奖赏和与奖赏相关事件的信息。有人提出，这种快速信号实际上可能是由共释放的谷氨酸传递的。多巴胺神经元共释放谷氨酸的证据主要来自于涉及培养神经元或幼年动物组织的研究。然而，最近的研究表明，这种双重谷氨酸能/多巴胺能表型随着年龄的增长而下降，并可因损伤而诱导，这表明它不是成年多巴胺神经元的一个关键特征。在这里，我们通过进一步表明，成年纹状体的亚区中的多巴胺能轴突和末梢不表达囊泡谷氨酸转运体（VGluT1、VGluT2 或 VGluT3），为这一观点提供了进一步的支持。从成年大鼠的纹状体组织中免疫标记酪氨酸羟化酶（TH；多巴胺的生物合成酶）和三种已知的 VGluTs 之一。重要的是，我们在电子显微镜水平上比较了与 TH 阳性结构相关的每一种 VGluT 的免疫金标记与背景标记。此外，我们对伏隔核的核心和壳进行了亚区分析。我们发现，背外侧纹状体和腹侧纹状体（伏隔核核心和壳）中的多巴胺能轴突和末梢不表达 VGluT1、VGluT2 或 VGluT3。因此，我们得出结论，在正常的成年大鼠纹状体中，多巴胺能轴突不共释放谷氨酸。
