Fig. 5: Inhibition of LC-NE projections to the CB impairs auditory fear conditioning.

a Inhibitory DREADD hM4D(Gi)-mCherry or control YFP virus were bilaterally injected in the LC of TH-Cre mice. CNO (300 nM) or saline was delivered into the CB vermis (created with BioRender.com). b DAPI-stained cerebellar slice showing the cannula placement (right) and corresponding stereotaxic atlas page (left). Scale bar, 500 μm. The image is representative of at least four replicates per experimental conditions. c, d Gi-DREADD (green) and TH (red) double labeling of LC neurons and their projections to CB. GL granular layer. Scale bar, 50 μm. Each image is representative of at least four replicates per experimental conditions. e DREADD-mediated inhibition of LC-CB projections during fear conditioning reduced the freezing response to the recall tone (two-way ANOVA followed by Sidaks test: treatment factor (F(1, 18) = 8.376, P = 0.0097), viral expression factor (F(1, 18) = 4.632, P = 0.0452), interaction factor (F(1, 18) = 4.589, P = 0.0461); n = 7 mice treated with hM4Di/CNO, n = 6 mice treated with hM4Di/vehicle, n = 5 mice treated with YFP/CNO, n = 4 mice treated with YFP/vehicle. Measurement of the total distance (f) and speed (g) in the open field revealed no difference between hM4Di/CNO mice with respect to control mice (YFP and vehicle); n = 7 mice treated with hM4Di/CNO, n = 7 mice treated with hM4Di/vehicle, n = 6 mice treated with YFP/CNO, n = 5 mice treated with YFP/vehicle. h Number of footslip errors in narrow beam walking test showed no significant motor coordination impairment in hM4Di/CNO mice compared to control mice (YFP and vehicle); n = 8 mice treated with hM4Di/CNO, n = 7 mice treated with hM4Di/vehicle, n = 4 mice treated with YFP/CNO, n = 3 mice treated with YFP/vehicle. Data are presented as mean values ± SEM. Source data are provided as Source Data file.