23077
There was no evidence that PQ induced neuronal degeneration in the SNpc or degenerating neuronal processes in the striatum , as indicated by the absence of uptake of silver stain or reduced immunolabeling of tyrosine - hydroxylase - positive ( TH ( + ) ) neurons .
 silver, tyrosine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 silver, tyrosine