ERBB4 and columnar cell hyperplasia of the breast: We found that: (1) the expression of NRG1 and pErbB4/ErbB4 peaked in the acute phase and then decreased in the chronic phase of CCH; (2) ErbB4 expressed neurons and selective types of GABAergic cells decreased after CCH, but the distribution pattern of ErbB4 remained unchanged; and (3) the expression of hippocampal NRG1/ErbB4 positively correlated with the degree of neuronal apoptosis (both NeuN/TUNEL immunostaining and caspase-3 activity), but not with glial activation according to Pearson’s correlation.