27270
This pre - treatment also induced a significant attenuation of the norepinephrine - induced contraction in a concentration - dependent manner ( Emax : 72 . 7 % of inhibition for 3mg / ml and 27 % de inhibition for 1mg / ml ) in a Ca ( 2 + ) free medium .
 norepinephrine, Ca ( 2 + )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 norepinephrine, Ca ( 2 + )