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Conclusion. The present study demonstrated the age-related decrease in the axonal diameter of the olfactory nerve. This finding may represent the maturational change of the olfactory receptor neurons. Objectives. The aim of this study was to investigate age-related changes in the axonal diameter of the olfactory nerve in the lamina propria. Materials and methods. Female ICR mice, postnatal age 10 days, 3 months, 7 months, and 16 months, were studied. The electron micrographs of septal olfactory mucosa were used to measure the axonal diameters of olfactory nerves. Results. The distribution of the diameter shifted toward the thinner side between 10-day-old and 3-month-old mice. The axonal diameter showed significant decreases (p < 0.001) from the age of 10 days to that of 3 months. [ABSTRACT FROM AUTHOR]

In a previous study we showed that, in rat spiral ganglion neurons (SGNs), the adenosine 5'-triphosphate (ATP)-evoked currents were a combination of the activation of ionotropic receptors (the first fast current) and the activation of metabotropic receptors which secondarily opened non-selective cation channels. These two conductances imply the involvement of different receptor subtypes. In the present study, we tested three subtype-specific purinergic ligands: α,β-methylene ATP (α,β-meATP) for P2X receptors, uridine 5′-triphosphate (UTP) for P2Y receptors and 2′-3′-O-(4-benzoylbenzoyl) ATP (Bz-ATP) for P2Z (P2X 7 ) receptors. Application of 100 μM α,β-meATP did not trigger any significant change in membrane conductance, while the SGNs were responsive to ATP. Pressure application of UTP (100 μM, 1 s) evoked an inward current averaging 344±169 pA at a holding potential of -50 mV. The conductance developed after a latency averaging 1.5±0.6 s, took 4-6 s to peak and reversed slowly within 15-30 s. The current-voltage curve reversed near 0 mV, suggesting a non-selective cation conductance, like the second component of the ATP conductance. Bz-ATP evoked an inward current which developed without latency, was sustained during ligand application and was rapidly inactivated at the end of application: the same characteristics as the first component of the ATP-evoked current. The Bz-ATP conductance reversed around -10 mV, indicating also a non-selective cation conductance. These results suggest that, in SGNs, ATP acts via two different receptor subtypes, ionotropic P2Z receptors and metabotropic P2Y receptors, and that these two receptor subtypes can assume different physiological roles. [ABSTRACT FROM AUTHOR]