20364
However , sigma 1 - KO mice exhibited an enhanced mechanical antinociception in response to systemic morphine ( 1 - 16 mg / kg ) .
 Chemical: morphine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: morphine