4356
Furthermore , interfering with EphA4 forward signaling using EphA4 - Fc blocked activity - induced homeostatic synaptic scaling - down , while direct activation of EphA4 with its ligand EphrinA1 weakened excitatory synaptic strength .
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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