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Sodium thiopenthal was administered intraperitoneally into male rats pre - treated with melatonin ( 0 . 05 , 0 . 5 , 5 and 50 mg / kg ) .
 Chemical: Sodium thiopenthal; Chemical: melatonin
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: Sodium thiopenthal; Chemical: melatonin