3996
With culture time increment , the firing rate of spontaneous action potential ( sAP ) in NRVMs was gradually decreased until spontaneous early after - depolarization ( EAD ) was observed after about one week culture .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None