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Morphine withdrawal induced the phosphorylation of the epigenetic factor methyl - CpG - binding protein 2 ( MeCP2 ) in Ser421 both in the LS and the NAc shell .
 Chemical: Morphine; Chemical: methyl; Chemical: CpG; Chemical: Ser421
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; Chemical: methyl; Chemical: CpG; Chemical: Ser421