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The purpose of this study was to evaluate an adjunctive treatment strategy to memory enhancement , namely combining the commonly prescribed acetylcholinesterase inhibitor ( AChEI ) donepezil , with a positive allosteric modulator ( PAM ) of alpha 7 nicotinic - acetylcholine receptors ( alpha 7 - nAChRs ) , PNU - 120596 .
 Chemical: donepezil; Chemical: acetylcholine; Chemical: PNU - 120596
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: donepezil; Chemical: acetylcholine; Chemical: PNU - 120596