Figure 3:

Neuromedin B (NMB) is required for signaling sneezing. (A) Single-cell RT-PCR was performed on individual Trpv1⁺ nasal sensory neurons that were labeled by intranasal application of fluorescent retrograde axonal tracer. Vesicular glutamate transporter 2 (Vglut2) and neuropeptides NMB (Nmb), CGRP (Calca), and substance P (Tac1) are selectively expressed by a majority of Trpv1⁺ nasal neurons. In contrast, Vesicular glutamate transporter 1 and 3 (Vglut1 and Vglut3), gastrin-releasing peptide (Grp), natriuretic peptide B (Nppb), and somatostatin (Sst) are expressed by few or no Trpv1⁺ nasal neurons. Whole trigeminal ganglia (TG) were used as a positive control. Genomic DNA served as a negative control (−) for intron-spanning primers used for RT-PCR. (B-D) Deficiency in VGLUT2 (Vglut2), substance P (Tac1), or CGRP (Calca) does not affect the sneezing response to aerosolized capsaicin solution (12 μM), compared with control mice. (E) Deficiency in the neuropeptide NMB (Nmb) abolishes the sneezing responses to aerosolized capsaicin (12 μM) and histamine (100 mM) solution. (F-G) Nmb deficiency abolishes the sneezing responses to serotonin (5-HT, aerosolized solution (1 mM), F) and neuropeptide FF solution (NPFF, 20 nmol in 2 μl, G). (H) In acute allergic model, the sneezing responses to allergen (ovalbumin, OVA, 0.2 μg in 2 μl PBS/nostril) were abolished in mast cell-deficient Kit^w-sh mice, compared with WT controls. This mast cell-dependent allergic sneezing was eliminated in Nmb^−/− mice. (I) Nmb^−/− mice display reduced sneezing response in chronic allergic model, compared with WT controls. The red arrow indicates the intranasal instillation of allergen (ovalbumin, OVA, 0.2 μg in 2 μl PBS / nostril) for sneezing test after five days of intranasal sensitization. (J) Inverse dose-response relationship between capsaicin and sneezing responses in WT mice. Nmb^−/− mice display reduced sneezing responses to capsaicin at all the doses tested. (K) Pain-related nose wiping behavior elicited by high-dose capsaicin (250 μM) remains intact in the Nmb^−/− mice, as in WT mice. (L) Capsaicin induces mouse apnea responses in a dose-dependent manner. Each dot represents an individual mouse (n=5–10 mice/group). Data are represented as mean ± SEM. ** P≤0.01, ***P≤0.001, n.s. not significant. See also Figure S2.