Function of dopamine transporter is compromised in DYT1 transgenic animal model in vivo
Function of dopamine transporter is compromised in DYT1 transgenic animal model in vivo
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DOI：
10.1111/j.1471-4159.2010.06590.x
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发表时间：
2010-04-01
影响因子：
4.7
通讯作者：
Balcioglu, Aygul
中科院分区：
文献类型：
--
作者：
Hewett, Jeff;Johanson, Peter;Balcioglu, Aygul
早发性扭转肌张力障碍（DYT1）是遗传性原发性肌张力障碍最常见的形式，是由TOR1A基因突变引起的，该基因编码torsinA蛋白。我们之前在传统的DYT1肌张力障碍转基因小鼠模型（hMT1）中检测了人突变体torsinA对纹状体多巴胺能功能的影响，其中人突变体torsinA在巨细胞病毒启动子下表达。与野生型转基因和非转基因小鼠相比，这些小鼠全身服用安非他明并没有有效地增加多巴胺（DA）的释放。现在，我们利用体内无净通量微透析研究了DA转运体（DAT）在hMT1转基因小鼠中对安非他明诱导的DA释放的贡献。该方法通过微透析探针应用不同浓度的DA，并在平衡期后测量探针输出处的DA浓度。斜率（提取分数）是体内DAT活性的度量。hMT1转基因小鼠的斜率为0.58 +/- 0.07，非转基因小鼠的斜率为0.87 +/- 0.06 （p < 0.05）。我们进一步研究了诺非芬辛（一种特异性的DAT抑制剂）抑制安非他明诱导的DA释放的功效。在全身应用安非他明前80分钟局部应用诺米芬，可抑制转基因小鼠及其非转基因幼崽DA的释放。hMT1转基因小鼠的平均抑制率为48%，而非转基因小鼠的平均抑制率为84%。此外，我们使用o型迷宫行为室评估了hMT1转基因小鼠与非转基因小鼠的基础运动和安非他明诱导的运动。hMT1转基因小鼠的基础运动水平显示，它们的运动速度远低于非转基因小鼠（转基因小鼠0.9 +/- 0.3 m比非转基因小鼠2.4 +/- 0.7 m, p < 0.05）。在服用安非他明后，这种运动的相对减少也被观察到（转基因组为48.5 +/- 6.7 m，非转基因组为73.7 +/- 9.8 m, p < 0.05）。这些结果支持了一项发现，即hMT1转基因小鼠体内DA释放和再摄取的动力学改变，突变torsinA存在时DAT活性降低，这与行为后果一致，如运动减少和（先前描述的）异常运动表型，如后基宽度增加和在抬梁任务中的表现受损。这些数据表明，在人DYT1肌张力障碍中，DAT功能的改变可能导致DA神经传递受损和临床症状。
P>Early onset torsion dystonia (DYT1), the most common form of hereditary primary dystonia, is caused by a mutation in the TOR1A gene, which codes for the protein, torsinA. We previously examined the effect of the human mutant torsinA on striatal dopaminergic function in a conventional transgenic mouse model of DYT1 dystonia (hMT1), in which human mutant torsinA is expressed under the cytomegalovirus promotor. Systemic administration of amphetamine did not increase dopamine (DA) release as efficiently in these mice as compared with wild-type transgenic and non-transgenic mice. We, now, studied the contribution of the DA transporter (DAT) to amphetamine-induced DA release in hMT1 transgenic mice using in vivo no-net flux microdialysis. This method applies different concentrations of DA through the microdialysis probe and measures DA concentration at the output of the probe following an equilibrium period. The slope (extraction fraction) is the measure of the DAT activity in vivo. The slope for hMT1 transgenic mice was 0.58 +/- 0.07 and for non-transgenic animals, 0.87 +/- 0.06 (p < 0.05). We further investigated the efficacy of nomifensine (a specific DAT inhibitor) in inhibiting amphetamine-induced DA release. Local application of nomifensine 80 min before the systemic application of amphetamine inhibited DA release in both transgenic mice and their non-transgenic littermates. The efficiency of the inhibition appeared to be different, with mean values of 48% for hMT1 transgenic mice versus 84% for non-transgenic littermates. Moreover, we have evaluated basal and amphetamine-induced locomotion in hMT1 transgenic mice compared with their non-transgenic littermates, using an O-maze behavioral chamber. Basal levels of locomotion in the hMT1 transgenic mice showed that they moved much less than their non-transgenic littermates (0.9 +/- 0.3 m for transgenic mice vs. 2.4 +/- 0.7 m for non-transgenic littermates, p < 0.05). This relative reduction in locomotion was also observed following amphetamine administration (48.5 +/- 6.7 m for transgenics vs. 73.7 +/- 9.8 m for non-transgenics, p < 0.05). These results support the finding that there are altered dynamics of DA release and reuptake in hMT1 transgenic mice in vivo, with DAT activity is reduced in the presence of mutant torsinA, which is consistent with behavioral consequences such as reduced locomotion and (previously described) abnormal motor phenotypes such as increased hind-base width and impaired performance on the raised-beam task. These data implies that altered DAT function may contribute to impaired DA neurotransmission and clinical symptoms in human DYT1 dystonia.