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OBJECTIVES : To investigate the ability of naltrexone and beta - funaltrexamine , an irreversible mu - opioid specific antagonist , to inhibit ethanol - stimulated and morphine - stimulated mesolimbic dopamine release , and to determine whether opioid receptors on mesolimbic neurons contribute to these mechanisms .
 Chemical: naltrexone; Chemical: beta - funaltrexamine; Chemical: ethanol; Chemical: morphine; Chemical: dopamine
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: naltrexone; Chemical: beta - funaltrexamine; Chemical: ethanol; Chemical: morphine; Chemical: dopamine