Bannon M J, Poosch M S, Xia Y, Goebel D J, Cassin B, Kapatos G
Department of Psychiatry (Cellular and Clinical Neurobiology Program), Wayne State University School of Medicine, Detroit, MI.
Proc Natl Acad Sci U S A. 1992 Aug 1;89(15):7095-9. doi: 10.1073/pnas.89.15.7095.
The dopamine transporter is the primary means of inactivating synaptic dopamine as well as a major site of action for psychostimulants (such as cocaine and amphetamine) and for neurotoxins that induce parkinsonism. In the present study, a human dopamine transporter partial cDNA clone obtained by polymerase chain reaction exhibited 87% and 89% identity at the nucleic acid and amino acid levels, respectively, with transmembrane domains 3-5 of the rat homolog. This clone was used to quantitate human dopamine transporter mRNA by nuclease protection assay. The postmortem content of dopamine transporter mRNA in the substantia nigrae of 18- to 57-yr-old subjects was relatively constant, while in subjects greater than 57 yr old, a precipitous (greater than 95%) decline in substantia nigra dopamine transporter mRNA was evident. In contrast, tyrosine hydroxylase mRNA in the same samples declined in a linear manner with increasing age. In situ hybridization experiments confirmed the profound loss of dopamine transporter gene expression in melanin-positive (presumptive dopamine) nigral neurons. These data may begin to shed light on compensatory changes occurring in human dopamine neurons during normal aging.
多巴胺转运体是使突触多巴胺失活的主要方式，也是精神兴奋剂（如可卡因和苯丙胺）以及诱发帕金森症的神经毒素的主要作用位点。在本研究中，通过聚合酶链反应获得的人多巴胺转运体部分cDNA克隆，在核酸水平和氨基酸水平上，分别与大鼠同源物的跨膜结构域3 - 5具有87%和89%的同一性。该克隆用于通过核酸酶保护试验定量人多巴胺转运体mRNA。18至57岁受试者黑质中多巴胺转运体mRNA的死后含量相对恒定，而在大于57岁的受试者中，黑质多巴胺转运体mRNA明显急剧下降（大于95%）。相比之下，同一样本中的酪氨酸羟化酶mRNA随年龄增长呈线性下降。原位杂交实验证实了黑色素阳性（推测为多巴胺能）黑质神经元中多巴胺转运体基因表达的显著丧失。这些数据可能开始揭示正常衰老过程中人类多巴胺能神经元发生的代偿性变化。
