Fig. 4: Blockade of brain drainage pathway prevents the effects of 40 Hz blue light treatment.

a The experimental timeline of the surgical ablation of the lymphatic afferent vessels to the deep cervical lymph nodes (dCLNs), blue light treatment, behavioral tests, injection of the OVA-Alexa Fluor 647 tracer into the cisterna magna (i.c.m.) and sacrifice (sac). b Representative images depicting OVA tracer (red) and DAPI staining (blue) in the dCLNs. Scale bar, 250 μm. c Quantification of the fluorescence intensity and the percentage of area covered by the OVA tracer in the dCLNs (n = 8, 9, 6). d The spontaneous alternation and total numbers of arm entries in the Y-maze test (n = 7, 9, 6). e Representative heatmaps of animals’ traveling paths during the test session of the novel object recognition (NOR). f Quantification of the discrimination index (DI) and the total time spent on exploring both objects (total exploration) during the training and the test sessions of NOR (n = 7, 9, 6). AD-Con-Sham, 5xFAD mice that did not receive blue light treatment and lymphatic vessel ablation; AD-BLUE-Sham, 5xFAD mice that received blue light treatment but did not receive lymphatic vessel ablation; AD-BLUE-Ablation, 5xFAD mice that received blue light treatment and lymphatic vessel ablation. All data are presented as the mean ± SEM and analyzed by one-way ANOVA followed by Tukey’s (c, f, d, total entries) or Fisher’s LSD (d, spontaneous alteration) post hoc tests.