Even before hearing becomes active, there is a transient cholinergic innervation in the developing mammalian inner ear. The physiological significance of these synapses has never been demonstrated. Glowatzki and Fuchs show that the novel neuronal nicotinic acetylcholine receptor α9 is functionally present in neonatal cochlear inner hair cells and behaves like a true acetylcholine receptor. Its stimulation results in the activation of a fast, calcium-dependent potassium channel. Acetylcholine thus inhibits afferent activity and acts to impose rhythmicity onto the immature auditory pathway.
Glowatzki, E., and Fuchs, P.A. (2000) Cholinergic synaptic inhibition of inner hair cells in the neonatal mammalian cochlea. Science 288: 2366-2368. [Abstract] [Full Text]
