2748
We conclude that the analgesic action of opioids on the peripheral terminals of primary afferents is via a binding site with characteristics of the mu - opioid receptor and that this action is mediated by inhibition of the cyclic adenosine monophosphate second messenger system .
 Chemical: cyclic adenosine monophosphate
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: cyclic adenosine monophosphate