Dopamine itself can't cross the blood-brain barrier, but its precursor levodopa can, and once in the brain, levodopa is converted to dopamine by dopa decarboxylase, most importantly within the remaining nigrostriatal neurons.

胺本身不血脑屏障，但它的前体左旋可以，一旦入脑中，左旋就会被脱羧酶转换胺，尤其是在残存的黑质纹状体神经元内。

I don't have to keep saying nigrostriatal and mesocortical.

我不必一直说黑质纹状体和中皮质。