2699
The present experiments were designed to investigate the role of the midline cells of the B3 serotonin neurons in the medulla , coinciding with the raphe magnus .
 Chemical: serotonin
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: serotonin