2225
In previous studies , we have characterized three new synthesized guanidine and 2 - aminoimidazoline aromatic derivatives ( 8b , 17b and 20b ) as alpha 2 - adrenoceptor antagonists that are able to increase extracellular concentration of noradrenaline in rat brain .
 Chemical: guanidine; Chemical: 2 - aminoimidazoline; Chemical: noradrenaline
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: guanidine; Chemical: 2 - aminoimidazoline; Chemical: noradrenaline