16844
Pretreatment of the cells with 4 - aminopyridine , a selective blocker of IA , abolished this effect .
 Chemical: 4 - aminopyridine
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: 4 - aminopyridine