Fig. 7: Involvement of brain locus coeruleus in the SNS-controlled tear reduction.

a Schematic diagram of retrograde trans-synaptic tracing and representative images of RFP signals in locus coeruleus (LC) and GFP signals in superior salivatory nucleus (SSN). Created in BioRender. Wang, Q. (2025) https://BioRender.com/a9nx90z. Scale bar, 100 μm. The experiment was repeated at least three times independently with a similar result. b, c Representative images and quantitative analysis of c-FOS⁺TH⁺ neurons in LC and c-FOS⁺ChAT⁺ neurons in SSN (n = 4 mice per group. LC P = 0.0050, SSN P < 0.0001). Scale bar, 100 μm. d Representative trace of patch-clamp recording and quantification of action potential frequency under 60 pA current injection for LC neurons in the SCOP-treated mice and vehicle mice (Ctrl: n = 6 cells, SCOP: n = 5 cells. P = 0.0476). e Schematic diagram of chemogenetic inhibition in LC of Th-cre mice. Created in BioRender. Wang, Q. (2025) https://BioRender.com/ntcf4so. f Representative images and quantitative analysis of c-FOS⁺TH⁺ neurons in LC after chemogenetic manipulation (n = 5 mice per group. P < 0.0001). Scale bar, 100 μm. g In vivo electrophysiological recordings of LC neurons in scopolamine-treated hM4Di expressing mice after CNO or NaCl injection. Representative example rasters (upper panel) and rate histogram (lower panel) of LC neurons in mice treated with CNO or NaCl. h Tear secretion of scopolamine-treated hM4Di expressing mice with CNO or NaCl injection (n = 10 eyes per group. P < 0.0001). i Schematic diagram of optogenetic manipulation of LC neurons in Th-cre mice. Created in BioRender. Wang, Q. (2025) https://BioRender.com/mz65rvu. j Neuronal identification of AAV9-EF1a-DIO-eNpHR3.0-EYFP in Th-cre mice. The LC noradrenergic neurons (TH) labeled by AAVs (EYFP). Scale bar, 100 μm. The experiment was repeated at least three times independently with a similar result. k Tear secretion of Th-cre mice after LC optogenetic manipulation by injecting AAV9-EF1a-DIO-eNpHR3.0-EYFP and control virus (EGFP: n = 6 eyes, eNpHR3.0: n = 8 eyes. 10 min P = 0.7374, 20 min P = 0.0003, 30 min P = 0.0005, 40 min P = 0.3973). The yellow area denotes the inhibition period. Data are shown as mean ± SEM. The significance of differences was detected using unpaired two-sided Student’s t test (c, f, h, k) or two-sided Mann-Whitney U test (d) *P < 0.05, **P < 0.01, ***P < 0.001. Source data are provided as a Source Data file.