FIGURE 3.

Determination of maximum volume to target the olfactory mucosa in C57Bl6 mice. (A–E) The parts lateral from the nasal septum had been removed carefully to give access to the olfactory region. The catheter was inserted to target the olfactory region and a fluorescein solution was applied in steps of 0.5 µL under UV illumination. (F) The maximum volume was determined when the fluorescein solution drained into the nasal passage as indicated with the arrowhead. This occurred during the increase of applied volume from 5.5 to 6 µL. Thus, the maximum volume for olfactory region-specific targeting was determined as 5 µL. (G) Insertion of a 10 µl pipette tip into the nasopharyngeal duct of the murine skull to simulate the murine breathing pattern with inhalation and exhalation. 20 simulated breath cycles with a volume of 100 µL each were performed within 10 s. The volume of fluorescein sodium that remained in the pipette after the last inhalation was quantified and denominated as the aspirated volume. (H) Determination of the dependency of the experimentally determined maximum volume and the recommended volume with the weight of the individual mouse cadavers. The was a significant correlation between experimentally determined volumes and individual weight (*p < 0.04, r ² = 0.43, n = 10).