21385
The involvement of alpha 4 beta 2 nAChR was supported by the lack of nicotine - induced structural remodeling in neurons from alpha 4 null mutant mice ( KO ) .
 Chemical: nicotine
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: nicotine