CHAT and columnar cell hyperplasia of the breast: Compared with the sham‐operation group, the levels of ACh and the activities of ChAT (p < .001, respectively, Figure 2a,b) in the cerebral cortices and hippocampi of rats in the saline treatment model group significantly decreased, while the activity of AChE (p < .001, respectively, Figure 2c) increased significantly, indicating that CCH causes central cholinergic dysfunction in rats.