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Ketamine exposure resulted in elevated NMDA receptor ( NR1 ) expression , increased generation of reactive oxygen species ( ROS ) as indicated by higher levels of 8 - oxoguanine production , and enhanced neuronal damage .
 Chemical: Ketamine; Chemical: NMDA; Chemical: oxygen; Chemical: 8 - oxoguanine
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: Ketamine; Chemical: NMDA; Chemical: oxygen; Chemical: 8 - oxoguanine