910
Pretreatment of mice with alpha - methyltyrosine ( 20 mg / kg i . p . , one hour ) , an inhibitor of tyrosine hydroxylase , significantly decreased the activity - increasing effects of morphine .
 alpha - methyltyrosine, tyrosine, morphine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 alpha - methyltyrosine, tyrosine, morphine