2746
The analgesic effect of the mu - agonist morphine was dose - dependently antagonized by naloxone and prevented by co - injection of pertussis toxin .
 Chemical: morphine; Chemical: naloxone
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: morphine; Chemical: naloxone