5698
We report that intra - PLC microinfusions of a selective D ( 1 ) receptor agonist block the spontaneous expression of an associative olfactory fear memory , without altering the stability of the original memory trace .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None