a, Mice infected with DREADD virus in CA1 were injected with saline (SAL) or clozapine-N-oxide (CNO) and then euthanized 90 min post-injection for immunofluorescence staining. b, There was no difference in the percentage of DREADD-positive cells (labelled with GFP) between SAL and CNO groups (unpaired t-test, t7 = 0.01, not significant, n = 3, 6 mice). c, DREADD-positive cells (labelled with GFP) had more ZIF when injected with CNO than SAL (unpaired t-test, t7 = 5.08, P = 002). d, Representative examples of ZIF, DREADD, DAPI as well as merged images of CA1. e, Design for elevated plus maze experiment in aged mice with DREADD virus. f, A two-way ANOVA showed no main effect of injection (F1,9 = 0.75, not significant, n = 6, 5 mice) and a significant main effect of arms (F1,9 = 71.03, P < 0.0001). There was no significant interaction between injection and arms (F1,9 = 0.003, not significant). Results show mean ± s.e.m.