852
These results indicate a possible involvement of endogenous opioid peptides in the cardiac effects due to myocardial ischaemia and reperfusion , mediated by opiate receptors through opiate antagonism .
 opiate receptors
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 opiate receptors