University of Ottawa Institute of Mental Health Research, affiliated with The Royal, Ottawa (Cassidy, Cheung); Department of Psychiatry, Columbia University College of Physicians and Surgeons, and New York State Psychiatric Institute, New York (Cassidy, Carpenter, Grassetti, Abi-Dargham, Martinez, Horga); Department of Psychiatry, Rutgers University, Piscataway, N.J. (Konova); Institute of Biomedical Technologies, National Research Council of Italy, Milan (Zecca); Department of Psychiatry, Stony Brook University, Stony Brook, N.Y. (Abi-Dargham).
Am J Psychiatry. 2020 Nov 1;177(11):1038-1047. doi: 10.1176/appi.ajp.2020.20010090. Epub 2020 Aug 28.
Recent evidence supports the use of neuromelanin-sensitive MRI (NM-MRI) as a novel tool to investigate dopamine function in the human brain. The authors investigated the NM-MRI signal in individuals with cocaine use disorder, compared with age- and sex-matched control subjects, based on previous imaging studies showing that this disorder is associated with blunted presynaptic striatal dopamine.
NM-MRI and T-weighted images were acquired from 20 participants with cocaine use disorder and 35 control subjects. Diagnostic group effects in NM-MRI signal were determined using a voxelwise analysis within the substantia nigra. A subset of 20 cocaine users and 17 control subjects also underwent functional MRI imaging using the monetary incentive delay task, in order to investigate whether NM-MRI signal was associated with alterations in reward processing.
Compared with control subjects, cocaine users showed significantly increased NM-MRI signal in ventrolateral regions of the substantia nigra (area under the receiver operating characteristic curve=0.83). Exploratory analyses did not find a significant correlation of NM-MRI signal to activation of the ventral striatum during anticipation of monetary reward.
Given that previous imaging studies show decreased dopamine signaling in the striatum, the finding of increased NM-MRI signal in the substantia nigra provides additional insight into the pathophysiology of cocaine use disorder. One interpretation is that cocaine use disorder is associated with a redistribution of dopamine between cytosolic and vesicular pools, leading to increased accumulation of neuromelanin. The study findings thus suggest that NM-MRI can serve as a practical imaging tool for interrogating the dopamine system in addiction.
最近的证据支持使用神经黑色素敏感 MRI（NM-MRI）作为一种新的工具来研究人类大脑中的多巴胺功能。作者根据先前的影像学研究结果，即该疾病与纹状体突触前多巴胺功能减退有关，对可卡因使用障碍患者与年龄和性别匹配的对照组个体的 NM-MRI 信号进行了研究。
从 20 名可卡因使用障碍患者和 35 名对照受试者中采集 NM-MRI 和 T1 加权图像。使用基于体素的分析方法在黑质内确定 NM-MRI 信号的诊断组效应。一小部分 20 名可卡因使用者和 17 名对照受试者还接受了使用金钱奖励延迟任务的功能 MRI 成像，以调查 NM-MRI 信号是否与奖励处理的改变有关。
与对照组相比，可卡因使用者的黑质腹外侧区域 NM-MRI 信号显著增加（受试者工作特征曲线下面积=0.83）。探索性分析未发现 NM-MRI 信号与预测金钱奖励时腹侧纹状体激活之间存在显著相关性。
鉴于先前的影像学研究显示纹状体中的多巴胺信号减少，黑质中 NM-MRI 信号增加提供了可卡因使用障碍病理生理学的更多见解。一种解释是，可卡因使用障碍与细胞溶质和囊泡池之间的多巴胺再分配有关，导致神经黑色素的积累增加。因此，研究结果表明 NM-MRI 可以作为一种实用的成像工具，用于探究成瘾中的多巴胺系统。
