BACKGROUND The dopamine (DA) neurotransmission has been implicated in fundamental brain functions, exemplified by movement controls, reward-seeking, motivation, and cognition. Although dysregulation of DA neurotransmission in the striatum is known to be involved in diverse neuropsychiatric disorders, it is yet to be clarified whether components of the DA transmission, such as synthesis, receptors, and reuptake are coupled with each other to homeostatically maintain the DA neurotransmission. The purpose of this study was to investigate associations of the DA synthesis capacity with the availabilities of DA transporters and D2 receptors in the striatum of healthy subjects. METHODS First, we examined correlations between the DA synthesis capacity and DA transporter availability in the caudate and putamen using PET data with L-[β-11C]DOPA and [18F]FE-PE2I, respectively, acquired from our past dual-tracer studies. Next, we investigated relationships between the DA synthesis capacity and D2 receptor availability employing PET data with L-[β-11C]DOPA and [11C]raclopride, respectively, obtained from other previous dual-tracer assays. RESULTS We found a significant positive correlation between the DA synthesis capacity and DA transporter availability in the putamen, while no significant correlations between the DA synthesis capacity and D2 receptor availability in the striatum. CONCLUSION The intimate association of the DA synthesis rate with the presynaptic reuptake of DA indicates homeostatic maintenance of the baseline synaptic DA concentration. In contrast, the total abundance of D2 receptors, which consist of presynaptic autoreceptors and postsynaptic modulatory receptors, may not have an immediate relationship to this regulatory mechanism.

中文翻译：

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活人脑中 PET 评估的多巴胺合成能力与多巴胺转运蛋白和 D2 受体可用性的差异关联

背景多巴胺 (DA) 神经传递与基本的大脑功能有关，例如运动控制、寻求奖励、动机和认知。尽管已知纹状体中 DA 神经传递的失调与多种神经精神疾病有关，但尚不清楚 DA 传递的组成部分（例如合成、受体和再摄取）是否相互耦合以稳态维持 DA 神经传递. 本研究的目的是调查 DA 合成能力与健康受试者纹状体中 DA 转运蛋白和 D2 受体的可用性之间的关联。方法一、我们分别使用 L-[β-11C]DOPA 和 [18F]FE-PE2I 的 PET 数据检查了尾状核和壳核中 DA 合成能力和 DA 转运蛋白可用性之间的相关性，这些数据是从我们过去的双示踪研究中获得的。接下来，我们分别使用 PET 数据与 L-[β-11C]DOPA 和 [11C]raclopride 研究了 DA 合成能力和 D2 受体可用性之间的关系，这些数据分别来自其他先前的双示踪剂测定。结果 我们发现壳核中 DA 合成能力与 DA 转运蛋白可用性之间存在显着正相关，而纹状体中 DA 合成能力与 D2 受体可用性之间没有显着相关性。结论 DA 合成速率与 DA 的突触前再摄取的密切关联表明基线突触 DA 浓度的稳态维持。相比之下，由突触前自身受体和突触后调节受体组成的 D2 受体的总丰度可能与这种调节机制没有直接关系。