30242
Electrophysiology studies show that this shift in palatability corresponds to an alteration in nucleus accumbens ( NAc ) cell firing ; neurons that previously responded with inhibition during infusion of the palatable sweet shifted to excitatory activity during infusion of the cocaine - devalued tastant .
 cocaine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 cocaine