6870
Here , we used electrophysiological and Na ( + ) imaging techniques to study the role of alpha 3 in central nervous system neurons expressing both isoforms .
 Chemical: Na ( + )
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: Na ( + ) 
Answer:
 Chemical: Na ( + )