SPATIO-TEMPORAL LOCALIZATION OF BETA TUBULIN III IN THE ORGAN OF CORTI AND IN THE SPIRAL GANGLIA BETWEEN THE EMBRYONIC DAY (E18) AND THE POST-NATAL DAY (P25) IN RAT.

The mammalian auditory organ, the organ of Corti (OC), is composed of mechanosensory hair cells and nonsensory supporting cell types. Based on their morphology and physiology, at least two types of sensory cells can be identified in the OC: inner and outer hair cells. The structure of this organ is well reported in adult but its development is still little-known.
By using confocal microscopy, we studied the spatial-temporal distribution of beta tubulin III during the differentiation of the OC in rat from the embryonic day 18 (E18) to the postnatal day (P25).
The beta tubulin III is typical for neural cells in the OC. We observed that beta III tubulin is present in the extensions innerving the row of inner hair cells at E18. At E19, the extensions innerving the inner hair cells and the two first rows of outer hair cells were immunolabelled. From E21 to P25, all of hair cells were connected to the spiral ganglion. In the latter, the intensity of immunolabelling decreased between E18 to P25 and the labelling only concerned some cells.
These results reveal that beta III tubulin appears before birth in the nervous extensions connecting the sensory cells of the OC according to a modiolar-to-striolar gradient. In the spiral ganglia, the labelling progressively decreases during its development.