7656
In vitro cultured neurons challenged with N - methyl - D - aspartate ( NMDA , 200 mu M ) for 30 min showed significant decrease in the viability of neurons ; however , OMT was able to protect neurons against induced neurotoxicity via NMDA exposure .
 N - methyl - D - aspartate, NMDA, OMT, NMDA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 N - methyl - D - aspartate, NMDA, OMT, NMDA