30450
Following a 21 day recovery period , chronic saline - and MPTP - treated mice received an additional injection of either saline ( 10 ml / kg ; s . c . ) or MPTP ( 20 mg / kg ; s . c . ) and were sacrificed 24 h later .
 MPTP, MPTP
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 MPTP, MPTP