Nara Institute of Science and Technology, 8916-5, Ikoma 630-0101, Japan.
Department of Biomedical Engineering, University of Houston, Houston, TX 77204-5060, USA.
Int J Mol Sci. 2022 Jan 20;23(3):1114. doi: 10.3390/ijms23031114.
Dopamine (DA) is the key regulator of reward behavior. The DA neurons in the ventral tegmental area (VTA) and their projection areas, which include the prefrontal cortex (PFC), nucleus accumbens (NAc), and amygdala, play a primary role in the process of reward-driven behavior induced by the drugs of addiction, including nicotine and alcohol. In our previous study, we developed a novel platform consisting of micro-LED array devices to stimulate a large area of the brain of rats and monkeys with photo-stimulation and a microdialysis probe to estimate the DA release in the PFC. Our results suggested that the platform was able to detect the increased level of dopamine in the PFC in response to the photo-stimulation of both the PFC and VTA. In this study, we used this platform to photo-stimulate the VTA neurons in both ChrimsonR-expressing (non-specific) wild and dopamine transporter (DAT)-Cre (dopamine specific) mice, and measured the dopamine release in the nucleus accumbens shell (NAcShell). We measured the DA release in the NAcShell in response to optogenetic stimulation of the VTA neurons and investigated the effect of GABAergic neurons on dopaminergic neurons by histochemical studies. Comparing the photo-stimulation frequency of 2 Hz with that of 20 Hz, the change in DA concentration at the NAcShell was greater at 20 Hz in both cases. When ChrimsonR was expressed specifically for DA, the release of DA at the NAcShell increased in response to photo-stimulation of the VTA. In contrast, when ChrimsonR was expressed non-specifically, the amount of DA released was almost unchanged upon photo-stimulation. However, for nonspecifically expressed ChrimsonR, intraperitoneal injection of bicuculline, a competitive antagonist at the GABA-binding site of the GABA receptor, also significantly increased the release of DA at the NAcShell in response to photo-stimulation of the VTA. The results of immunochemical staining confirm that GABAergic neurons in the VTA suppress DA activation, and also indicate that alterations in GABAergic neurons may have serious downstream effects on DA activity, NAcShell release, and neural adaptation of the VTA. This study also confirms that optogenetics technology is crucial to study the relationship between the mesolimbic dopaminergic and GABAergic neurons in a neural-specific manner.
多巴胺（DA）是奖励行为的关键调节因子。腹侧被盖区（VTA）中的 DA 神经元及其投射区域，包括前额叶皮层（PFC）、伏隔核（NAc）和杏仁核，在药物成瘾诱导的奖励驱动行为过程中发挥主要作用，包括尼古丁和酒精。在我们之前的研究中，我们开发了一个由微 LED 阵列设备组成的新型平台，通过光刺激和微透析探针来刺激大鼠和猴子的大脑大片区域，以估计 PFC 中的 DA 释放。我们的结果表明，该平台能够检测到 PFC 中多巴胺水平的升高，以响应 PFC 和 VTA 的光刺激。在这项研究中，我们使用该平台对表达 ChrimsonR（非特异性）的野生型和多巴胺转运体（DAT）-Cre（多巴胺特异性）小鼠的 VTA 神经元进行光刺激，并测量壳核（NAcShell）中的多巴胺释放。我们测量了 VTA 神经元光刺激引起的 NAcShell 中的 DA 释放，并通过组织化学研究调查了 GABA 能神经元对多巴胺能神经元的影响。比较 2 Hz 和 20 Hz 的光刺激频率，两种情况下 NAcShell 中的 DA 浓度变化在 20 Hz 时更大。当 ChrimsonR 特异性表达 DA 时，VTA 光刺激会导致 NAcShell 中的 DA 释放增加。相比之下，当 ChrimsonR 非特异性表达时，光刺激几乎不会改变 DA 的释放量。然而，对于非特异性表达的 ChrimsonR，腹腔内注射 GABA 受体 GABA 结合位点的竞争性拮抗剂——荷包牡丹碱，也会显著增加 VTA 光刺激引起的 NAcShell 中 DA 的释放。免疫化学染色的结果证实 VTA 中的 GABA 能神经元抑制 DA 激活，并且还表明 GABA 能神经元的改变可能对 DA 活性、NAcShell 释放和 VTA 的神经适应产生严重的下游影响。这项研究还证实，光遗传学技术对于以神经特异性方式研究中脑边缘多巴胺能和 GABA 能神经元之间的关系至关重要。
