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Among serotonin receptors , 5 - hydroxytryptamine 1B ( 5 - HT1B ) receptors have been associated with drug abuse including alcohol .
 serotonin, 5 - hydroxytryptamine, alcohol
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 serotonin, 5 - hydroxytryptamine, alcohol