Objective    To study the expression of aquaporin 1 (AQP1) in olfactory mucosa of mice and its effect on formation of olfaction.     Methods    Different expressions of AQP1 in olfactory mucosa of wild-type and AQP1-knocked out mice were detected by immunoblot and immunofluorescence. Different olfactory functions of mice were assayed by buried food pellet and olfactory maze test and by recording the electric potential on odorant-stimulated electroolfactogram (EOG)

respectively.      Results    Immunoblot and immunofluorescence showed that AQP1 was not expressed in olfactory mucosa of AQP1-knocked out mice. Immunofluorescence image revealed that AQP1 was mainly expressed in endothelial cells of blood vessels and in perineuria of olfactory lamina propria. Olfactory behavioral assay showed that the deference in time to find foods on days 1 and 2 of buried food pellet test was significant (P0.05). However

no difference was observed on day 3 between buried food pellet test and control test (P0.05). The difference in time to find foods was significant on all days of olfactory maze test (P0.05) but not of the control test (P0.05). The potential wave on odorant-stimulated EOG under different psi and the action of saturated trithylamine was similar in wild-type and AQP1-knocked out mice. The amplitude of odorant-stimulated electroolfactogram increased in a pressure-dependent manner. Under the same pressure

the amplitude of odorant-stimulated electroolfactogram was lower in AQP1-knocked out mice than in wild-type mice (P0.05).      Conclusion    AQP1 is mainly expressed in endothelial cells of blood vessels and in perineuria of olfactory lamina propria. Olfactory sensitivity is lower in AQP1-knocked out mice than in wild type mice with no difference in olfactory neuron excitability. AQP1 may play an important role in transmission of olfaction.