Salvatore Michael F, Apparsundaram Subbu, Gerhardt Greg A
Department of Anatomy and Neurobiology, Center for Sensor Technology, University of Kentucky Medical Center, Lexington, KY 40536, USA.
Neurobiol Aging. 2003 Dec;24(8):1147-54. doi: 10.1016/s0197-4580(03)00129-5.
Aging in rodents, monkeys, and man is correlated with a reduction in dopamine transporter (DAT) ligand binding and DAT function. Using Western blot techniques, we investigated whether the source of these age-related changes in DAT was correlated with decreases in DAT protein levels in the striatum, substantia nigra (SN), nucleus accumbens (NAc), and ventral tegmental area (VTA) of 6, 18, and 24-month-old male Fischer 344 rats. The relative levels of tyrosine hydroxylase (TH) were also determined in each region. In the striatum, we also assessed [3H]-DA uptake and DAT plasma membrane expression using a membrane-impermeant biotin analog in crude synaptosomes prepared from these age groups. There was no significant age-related difference in DAT immunoreactivity per total protein or per total TH in striatum, NAc, SN, or VTA. Significant age-related changes in TH were only seen in the VTA of the 24-month-old rats (approximately 60% decrease). However, [3H]-DA uptake and DAT protein recovered in the biotinylated fraction in 24-month-old rats were significantly decreased (approximately 30%) compared to 6-month-old animals in the striatal synaptosomes. These data suggest that age-related decreases in striatal DAT function and ligand binding are related to a decrease in plasma membrane expression of DAT and not a decrease in the steady-state levels of DAT protein or loss of dopaminergic neuropil.
啮齿动物、猴子和人类的衰老与多巴胺转运体（DAT）配体结合及DAT功能的降低相关。我们运用蛋白质免疫印迹技术，研究了6个月、18个月和24个月大的雄性Fischer 344大鼠纹状体、黑质（SN）、伏隔核（NAc）和腹侧被盖区（VTA）中，这些与年龄相关的DAT变化的根源是否与DAT蛋白水平的降低有关。同时还测定了每个区域中酪氨酸羟化酶（TH）的相对水平。在纹状体中，我们还使用一种膜不透性生物素类似物，评估了从这些年龄组制备的粗制突触体中的[3H]-多巴胺摄取和DAT质膜表达。纹状体、NAc、SN或VTA中，总蛋白或总TH中的DAT免疫反应性没有显著的年龄相关差异。仅在24个月大的大鼠的VTA中观察到TH有显著的年龄相关变化（约降低60%）。然而，与6个月大的动物相比，24个月大的大鼠纹状体突触体中生物素化部分的[3H]-多巴胺摄取和DAT蛋白显著降低（约30%）。这些数据表明，纹状体DAT功能和配体结合的年龄相关降低与DAT质膜表达的降低有关，而非DAT蛋白的稳态水平降低或多巴胺能神经纤维的丧失。
