Postnatal development of the rat organ of Corti

Abstract

The development of cochlear receptor cells and their supporting elements was studied by means of semi-thin and ultra-thin sections during the first postnatal weeks in the rat. The temporal and spatial patterns of the receptor cell development were investigated between the 4th and 24th days after birth. At approx. ten equidistant positions along the entire cochlear duct length of inner and outer hair cells, width of outer hair cell triad and stereocilia-length of the outer hair cells were quantitatively analyzed. Striking maturational changes take place before the 12th day after birth, that is, when the onset of hearing occurs. These changes are the formation of the tunnel of Corti, of the Nuel spaces, the appearance of filaments within the supporting elements and the change in cell shape of the hair cells. Between 4 days and 20 days after birth the maturation of outer hair cells is characterized by a decrease of organelles in the cytoplasm and establishment of the subsurface cistern. The quantitative analysis revealed a unique developmental pattern of the length of the outer hair cells, the width of the outer hair cell triad and the stereocilia length of the outer hair cells. Shortly after birth these structures have an almost constant size along the whole cochlear duct, but with increasing age the structures shorten at the cochlear base and enlarge at the apex. This pattern results in the establishment of a baso-apical gradient of the above mentioned structures. We assume that this baso-apical gradient is of central importance for the frequency representation.

Mechanotransduction current is essential for stability of the transducing stereocilia in mammalian auditory hair cells

“…Of note, similar heights of the tallest row stereocilia were reported in hamster OHCs at the same mid-cochlear location and the same age (P5) (Kaltenbach et al, 1994). Furthermore, throughout the 24 hr culturing of the mouse cochlear explants harvested at P4, we did not detect any height changes in the tallest row stereocilia in the mid-cochlear OHCs (data not shown), consistent with previous reports showing that OHC (but not IHC) stereocilia stop growing and reach a plateau at the ages of P2-P4 throughout most of the cochlea except at the very apex (Roth and Bruns, 1992; Kaltenbach et al, 1994). …”

Roles of the Espin Actin-Bundling Proteins in the Morphogenesis and Stabilization of Hair Cell Stereocilia Revealed in CBA/CaJ Congenic Jerker Mice

“…As hair cell differentiation proceeded, differences between the stereocilia of je/je and +/+ mice became more pronounced. For example, differences from +/+ controls were already more obvious in the base of the cochlea than in the apex at P0 (Figure 2A–2C, 2G–2I, 2M–2O and 2S–2U), in accordance with the base-to-apex gradient of hair cell differentiation along the cochlear spiral [9], [52]. Importantly, the stereocilia of je/je mice did not show the usual large increases in diameter between P0 and P10.…”

Hair Cell Transduction, Tuning, and Synaptic Transmission in the Mammalian Cochlea

“…Such attachment may serve as a tight mechanical coupling between the two structures, but the functional significance of the V-shaped organization is unknown. Multiple rows of stereocilia are arranged in a staircase pattern that increases in height from one edge to the other (Figure 4); the shape and dimensions of the bundle vary with position along the cochlea, with more numerous and shorter stereocilia in progressing from the apex to the base of the cochlea (170) (256). …”