7797
In addition , the expression of 5 - HT ( 1A ) mRNA was lower in the hippocampus , 5 - HT ( 1B ) mRNA was higher in the hippocampus and brainstem and SERT mRNA was higher in the brain stem of MRL / MpJ mice .
 5 - HT, 5 - HT
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 5 - HT, 5 - HT