3407
The results suggest that rigidity , which is assumed to be due to an action of morphine in the striatum , can be antagonized by another process leading to dopaminergic activation in the striatum .
 rigidity, morphine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 rigidity, morphine