6355
Additionally , direct evidence has been provided that D ( 2 ) and 5 - HT ( 2A ) receptors form physical heterocomplexes which exert a functional cross - talk , as demonstrated by studies on hallucinogen - induced signaling .
 5 - HT
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 5 - HT