Roger L J, Breese G R, Morell P
Brain Res. 1980 Sep 15;197(1):95-112. doi: 10.1016/0006-8993(80)90437-0.
Following stereotaxic injection of [35S]methionine into the substantia nigra of adult rats, there was rapid local incorporation of radioactivity into acid-insoluble material. Incorporation peaked by 4 h and then decreased. In contrast, acid-precipitable radioactivity in the corpus striatum (the major projection site of the substantia nigra) rose markedly between 1 and 8 h followed by a plateau period and another even more marked increase between 24 h and 6 days. Experiments involving injection of [3H]fucose gave similar results except that most of the acid-precipitable radioactivity in the striatum appeared in an early wave. In each case radioactivity in the contralateral striatum was less than 11% of that on the ipsilateral side. Stereotaxic injection of colchicine (20 microgram) into the nigrostriatal pathway (within the median forebrain bundle) blocked transport of [35S]protein and [3H]glycoprotein by 90% and 50%, respectively. In animals treated with 6-hydroxydopamine (6-OHDA; treated neonatally or as adults) the accumulation of striatal [35S]protein was reduced to 7 to 26% of control levels; striatal [3H]glycoprotein was also reduced, but not as much (29% to 73% of control). In control experiments, [3H]DOPA wa injected into the substantia nigra, and [3H]dopamine was measured in corpus striatum; 6-OHDA treatment reduced the amounts of striatal [3H]dopamine recovered to 3% of control values. The failure of colchicine or 6-OHDA to block transport of incorporated fucose as effectively as the transport of incorporated methionine is possible due to greater diffusion of fucose away from the injection site to non-dopaminergic nuclei projecting to the striatum. The molecular weight distribution of radioactive proteins at the substantia nigra and corpus striatum was analyzed by polyacrylamide gel electrophoresis. For both [35S]methionine and [3H]fucose, the gel electrophoretic pattern of radioactive proteins in the injection site (substantia nigra) was complex and did not change greatly between 2 h and 6 days. At the projection site (striatum) the electrophoretic distribution pattern was initially different from that of the substantia nigra, and changed markedly over the course of several days. In 6-OHDA-treated animals (treated neonatally or as adults), the bulk of proteins transported in nigro-striatal non-dopaminergic neurons appears to be very similar to that transported in the intact pathway in control rats. However, in striata of 6-OHDA-treated animals, a consistent reduction in striatal 35S- and 3H-radioactivitiy was observed in proteins with molecular weight from about 67,000 to 77,000. Assuming that the 6-OHDA treatment did not substantially affect the non-dopaminergic neurons, we interpret this to mean that some of the proteins in this molecular weight range are transported primarily by dopaminergic neurons.
向成年大鼠黑质进行立体定位注射[35S]甲硫氨酸后，放射性迅速在局部掺入酸不溶性物质中。掺入量在4小时达到峰值，然后下降。相比之下，纹状体（黑质的主要投射部位）中酸可沉淀放射性在1至8小时之间显著上升，随后是一个平稳期，在24小时至6天之间又有一次更为显著的增加。涉及注射[3H]岩藻糖的实验得到了类似的结果，只是纹状体中大部分酸可沉淀放射性出现在早期波峰中。在每种情况下，对侧纹状体中的放射性不到同侧的11%。向黑质纹状体通路（在前脑内侧束内）立体定位注射秋水仙碱（20微克）分别使[35S]蛋白质和[3H]糖蛋白的转运阻断了90%和50%。在用6-羟基多巴胺（6-OHDA；新生期或成年期处理）处理的动物中，纹状体[35S]蛋白质的积累减少到对照水平的7%至26%；纹状体[3H]糖蛋白也减少了，但程度没那么大（对照的29%至73%）。在对照实验中，将[3H]多巴注入黑质，并在纹状体中测量[3H]多巴胺；6-OHDA处理使回收的纹状体[3H]多巴胺量减少到对照值的3%。秋水仙碱或6-OHDA不能像阻断掺入甲硫氨酸的转运那样有效地阻断掺入岩藻糖的转运，可能是因为岩藻糖从注射部位扩散到投射到纹状体的非多巴胺能核的程度更大。通过聚丙烯酰胺凝胶电泳分析黑质和纹状体中放射性蛋白质的分子量分布。对于[35S]甲硫氨酸和[3H]岩藻糖，注射部位（黑质）放射性蛋白质的凝胶电泳图谱很复杂，在2小时至6天之间变化不大。在投射部位（纹状体），电泳分布图谱最初与黑质不同，并且在几天内有明显变化。在6-OHDA处理的动物（新生期或成年期处理）中，黑质纹状体非多巴胺能神经元中转运的大部分蛋白质似乎与对照大鼠完整通路中转运的蛋白质非常相似。然而，在6-OHDA处理动物的纹状体中，观察到分子量约为67,000至77,000的蛋白质中纹状体35S和3H放射性持续降低。假设6-OHDA处理对非多巴胺能神经元没有实质性影响，我们将此解释为该分子量范围内的一些蛋白质主要由多巴胺能神经元转运。
