Fig. 5

Cholinergic Tau accumulation inhibits MS-CA1 but not MS-CA3 cholinergic pathway. A-C Anterograde tracing MS-hippocampus circuit in C57BL/6 mice. The trans-synaptic H129-G4 virus was infused into the MS, after 2 days, EGFP expression was detected in the whole hippocampus (B Scale bar, 200 μm), including CA1, DG, CA3 (C Scale bar, 50 μm). D-F Anterograde tracing MS-hippocampus circuit in ChAT-Cre mice. AAV-DIO-ChR2-EGFP was infused into the MS for 3 weeks and EGFP + fibers were detected in the hippocampus (E Scale bar, 200 μm), especially in CA1, DG, CA3 subregions (F Scale bar, 50 μm). N = 3 mice per group. G, I Diagram for conducting cholinergic overexpression of hTau and retrograde tracing of MS-HP circuit. AAV-DIO-hTau was infused into the MS of ChAT-Cre mice to specifically overexpress hTau in cholinergic neurons, and CTB555 was infused in the hippocampal CA1 and CA3 respectively to retrogradely trace MS-CA1 and MS-CA3 circuit. H, J Fluorescence confirmation of CTB555 expression in the CA1 and CA3 and co-localization of retrograde CTB555 with ChAT + neurons in the MS. K, N, Q, T Diagram for patch recording of cholinergic neuron overexpression of hTau in MS of MS-HP circuit especially by retrograde tracing. K-M Overexpressing hTau significantly decreased the excitability of asymmetrically discharged cholinergic neurons (L frequency, two-way ANOVA group × current, F [9,250] = 3.336, P < 0.01) in MS-CA1 pathway without changing the amplitude (M unpaired t test, t = 1.154, df = 25, P > 0.05), RMP (M unpaired t test, t = 1.751, df = 25, P > 0.05) and half-width (M unpaired t test, t = 0.7100, df = 25, P > 0.05). N-P No significant differences in the excitability (O two–way ANOVA group × current, F [9,230] = 0.3313, P > 0.05), amplitude (P unpaired t test, t = 0.1154, df = 25, P > 0.05), RMP (P unpaired t test, t = 1.960, df = 23, P > 0.05) and half-width (R unpaired t test, t = 0.6674 df = 23, P > 0.05) were detected on the asymmetrically discharged cholinergic neurons in the MS-CA3 pathway between the two group. Q–V No significant differences were detected in symmetrically discharged cholinergic neurons after overexpressing hTau in MS-CA1 pathway (R frequency, two-way ANOVA group × current, F [9,150] = 1.265, P > 0.05) without changing the amplitude (S unpaired t test, t = 0.9928, df = 15, P > 0.05), RMP (S unpaired t test, t = 1.589, df = 15, P > 0.05) and half-width (S unpaired t test, t = 0.7321, df = 15, P > 0.05) and MS-CA3 group (U two–way ANOVA group × current, F [9,140] = 0.6888, P > 0.05), without changing amplitude (V unpaired t test, t = 1.358, df = 14, P > 0.05), RMP (P unpaired t test, t = 1.742, df = 14, P > 0.05) and half-width (R unpaired t test, t = 0.9857 df = 14, P > 0.05). W-X Quantitative analyses of the asymmetric cholinergic neurons in MS-CA1 and MS-CA3 pathways in ChAT-hTau and control groups. N = 6 mice per group. *P < 0.05, **P < 0.01 vs control group. Data were presented as mean ± SEM