[Maturation of postsynaptic acetylcholine receptors in cochlear outer hair cells].

Sound transduction in the inner ear is controlled by olivocochlear efferents terminating predominantly at outer hair cells (OHC). Development of efferent fibers and thereby of postsynaptic OHC receptors was studied immunohistochemically in 13 cochleae from fetal guinea pigs. The gestational ages of the animals ranged from gestational day (GD) 35 to GD 56. To visualize nicotinic acetylcholine receptors (nAChR), sera were used from myasthenia gravis patients with confirmed nAChR antibodies. At GD 53 no staining was observed, whereas at GD 58 a striking nAChR-immunoreactivity was found. In cochleae from adult animals postsynaptic receptors were visualized at the bases of all three rows of OHCs. The region of the inner hair cells (IHC) was not stained. The present results indicate that nAChRs in guinea pig cochleae develop between GD 53 and GD 58. Maturation of the postsynaptic nAChRs coincides with development of OHC motile properties.