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Our first aim was to study the effects of d - amphetamine infusions into the shell and core in order to understand their relative importance to reward and operant responding .
 Chemical: d - amphetamine
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: d - amphetamine