CCK and Alzheimer disease: In a knock-in mouse model of AD (App NL-F/NL-F), the CCK+ neurons showed aberrant hyperexcitability in the early stage of AD together with a gradual decline in the expression level of CCK, whereas in aged animals a significant decrease in the number of CCK+ cells was observed in the hippocampal CA1 area (Shi et al., 2020).