23623
Intra - dorsal hippocampus ( DH ) injections of 8 - hydroxy - 2 - ( di - n - propylamino ) tetralin ( 8 - OH - DPAT ) , a serotonin - 1A ( 5 - hydroxytryptamine ( 5 - HT ) - 1A ) receptor agonist , were previously shown to inhibit the expression of contextual fear when administered six hours after conditioning .
 Chemical: 8 - hydroxy - 2 - ( di - n - propylamino ) tetralin; Chemical: 8 - OH - DPAT; Chemical: serotonin; Chemical: 5 - hydroxytryptamine; Chemical: 5 - HT
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: 8 - hydroxy - 2 - ( di - n - propylamino ) tetralin; Chemical: 8 - OH - DPAT; Chemical: serotonin; Chemical: 5 - hydroxytryptamine; Chemical: 5 - HT