5248
When we assessed expression level of mu - opioid receptor ( MOR ) in the periaqueductal gray where the receptors are critical for analgesic effects , immunoreactivity of MOR was significantly higher in CCR5 KO mice than WT mice without change in phosphorylation level of the receptor .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None