17828
The limited available animal studies implicate a role for the alpha 5 and beta 4 nAChR subunits in nicotine dependence and withdrawal ; however studies focusing on the behavioral role of the alpha 3 beta 4 * nAChR receptor subtype in nicotine dependence are lacking .
 Chemical: nicotine; 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; Chemical: nicotine