15155
Glial cell line - derived neurotrophic factor ( GDNF ) is a potent growth factor essential to the development , survival , and function of dopaminergic neurons ( Airaksinen and Saarma 2002 ) .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None