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We therefore investigated the effects of combinations of commonly abused stimulant drugs ( cocaine , MDMA , 3 , 4 - methylenedioxyamphetamine ( MDA ) and meta - chlorophenylpiperazine ( mCPP ) ) on the function of the human alpha 1 beta 2 gamma 2 GABAA receptor ( hGABAA - R ) , expressed in Xenopus oocytes , using the two - electrode voltage - clamp technique .
 Chemical: cocaine; Chemical: MDMA; Chemical: 3 , 4 - methylenedioxyamphetamine; Chemical: MDA; Chemical: meta - chlorophenylpiperazine; Chemical: mCPP
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: cocaine; Chemical: MDMA; Chemical: 3 , 4 - methylenedioxyamphetamine; Chemical: MDA; Chemical: meta - chlorophenylpiperazine; Chemical: mCPP