ObjectiveTo investigate the expression and function of aquaporin-4(AQP4) in the olfactory system of mice.MethodsThe differences of AQP4 expression in olfaction system between wild-type and AQP4-null mice were studied by immunoblotting and immunofluorescence methods. The differences of mouse olfactory functions in the two groups were examined by two olfactory behavioral assays: the buried food pellet test and olfaction maze test, and the odorant-stimulated electroolfactogram (EOG) recording. ResultsThe results of immunoblotting and immunofluorescence showed no AQP4 expression in the olfactory system in AQP4-null mice. Immunofluorescence result also indicated that AQP4 was mainly distributed in the membrane of support cells, duct cells of Bowmann’s gland, basal cells of olfactory epithelium, membrane of Bowmann’s gland epithelial cells, olfactory sheath cells surrounding the olfactory bundles, and the membrane of cells in the olfactory bundle layer and glomeruler layer. The results of olfactory behavioral assay were significantly different between the two groups at all time points tested in both the olfaction maze test and the buried food pellet test (P<0.05). It was showed that the EOGs under different pressures of saturated trimethylamine had a similar shape in both groups, and the amplitude of EOGs increased with the increase of pressure. While under the same pressure, the EOG amplitude of AQP4-null mice was significantly lower than that of wild-type mice(P<0.05). ConclusionAQP4 is widely distributed in the olfactory system of mice, including the olfactory mucosa, olfactory nerve, and olfactory bulb, which can protect the olfactory neural bundle and facilitate neural signal transfer.