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It has been proposed that the mu - opioid receptor plays a role in ethanol reinforcement through modulation of ethanol - stimulated mesolimbic dopamine release .
 Chemical: ethanol; Chemical: ethanol; 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: ethanol; Chemical: ethanol; Chemical: dopamine