Postnatal maturation of the organ of Corti in gerbils: Morphology and physiological responses

Abstract

The organ of Corti, the sensory epithelium of hearing in mammals, matures postnatally in the gerbil. Quantitative analyses of the postnatal development of the organ of Corti, including supporting cells and the basilar membrane, were carried out. The morphological study confirmed that maturation of the sensory cells proceeds with a base-to-apex gradient, with the outer hair cells appearing to mature before the inner hair cells. Maturation of the supporting cells and the basilar membrane commenced first in the middle turn. Expansion of the second row of Deiters' cells began at 6 days after birth in the middle turn, before enlargement of the pillar cell heads at 8 days postnatally. Pillar cell head enlargement continued until 20 days postnatally in the middle turn. The tunnel of Corti and spaces of Nuel appeared first in the middle turn between 8 and 10 days postnatally. The maturation of the basilar membrane involved the thickening of the central hyaline layer and a reduction in the epithelial cells on the tympanic aspect. This process continued until about 20 days after birth. The cochlear microphonic potential, whole nerve action potential, and stimulus frequency otoacoustic emissions were recorded from 12 days after birth onward and related to changes in organ of Corti morphology. The results show that changes in the accessory structures continue throughout the period of onset and development of cochlear responses between 12 and 20 days after birth, and may therefore influence the micromechanical responses of the organ of Corti to acoustic stimuli during this period.

Spatio-temporal dynamics of β-tubulin isotypes during the development of the sensory auditory organ in rat

“…This localization remained the Our results also showed the appearance, at birth, of this β4-tubulin isotype in the upper part of the inner pillar cell. The labelling in the upper part of the pillar cell was consistent with the finding that inner pillar assembly begins with the nucleation of a large microtubule population at the apical end of each cell (Tucker et al 1992;Souter et al 1997;Jensen-Smith et al 2003). These results were also in agreement with our electron microscopy analysis of pillar cells at P4 (Fig S9).…”

Development of the base of the cochlea: place code shift in the gerbil

“…The motility of outer hair cells was found to be essentially mature by 12 days of age in gerbils (He et al, 1994), consistent with the relative maturity of the cochlear ampli¢er in the base. In contrast, signi¢cant changes were found in the morphology of the organ of Corti in the base after 12 days of age in the same species (Schweitzer et al, 1996;Souter et al, 1997). The changes observed, a decrease in cross-sectional area and an increase in ¢ber thickness, are consistent with a graded increase in the passive resonant frequency of the basilar membrane in the base of the cochlea, over the period 12 days to adult in the gerbil.…”

How to Bury the Dead: Elimination of Apoptotic Hair Cells from the Hearing Organ of the Mouse

“…In ro-dents, structural maturation takes place early postnatally, just before the onset of hearing (Souter et al 1997). We hypothesized that the unique structural features of the mature organ of Corti bring about specializations in wound healing.…”