Expression of glycine receptors and gephyrin in the rat cochlea

The cochlear efferent feedback system exerts direct impact on cochlear nerve activity and balances interaural sensitivity. So far, acetylcholine, GABA and dopamine are known to be transmitters of the inhibitory efferent system. Despite the wealth of information about glycinergic neurotransmission in the central auditory system, the inhibitory glycine receptor (GlyR) has not yet been regarded as a target molecule of efferent transmission in the cochlea. Using RT-PCR, in situ hybridization and immunohistochemistry, we show that GlyRα3, GlyRβ and gephyrin are expressed in the organ of Corti and spiral ganglion neurons. Furthermore, two alternative splice variants of GlyRα3, corresponding to the long (α3_L) and short (α3_K) human isoforms, could be distinguished. The localization of glycine receptors below inner hair cells and in outer hair cells of the adult cochlea suggests that these inhibitory receptors may serve as target molecules of the efferent olivocochlear bundle.