McGeer P L, McGeer E G, Suzuki J S
Arch Neurol. 1977 Jan;34(1):33-5. doi: 10.1001/archneur.1977.00500130053010.
Measurements on human brain samples of some enzymes concerned with neurotransmitter synthesis suggest serious losses with age. The most severe loss found was that in striatal tyrosine hydroxylase activity, the rate-controlling enzyme in the synthesis of dopamine. Cell counts in the substantia nigra where this dopaminergic tract originates suggest that the decrease in enzyme activity is partly due to cell loss, but must largely reflect decreased activity of residual cells. It is possible that this loss may account for some of the difficulties in movement seen in aged individuals and that it might be less if pigment formation in these cells could be inhibited.
对一些与神经递质合成相关的酶在人脑样本中的测量表明，这些酶的活性会随着年龄的增长而严重丧失。所发现的最严重的活性丧失发生在纹状体酪氨酸羟化酶活性方面，该酶是多巴胺合成中的速率控制酶。这条多巴胺能通路起始的黑质中的细胞计数表明，酶活性的降低部分是由于细胞丢失，但在很大程度上必定反映了残留细胞活性的下降。这种活性丧失有可能是老年人出现某些运动困难的部分原因，并且如果能够抑制这些细胞中的色素形成，这种活性丧失可能会减轻。
