Cochlear homeostasis: a molecular physiological perspective on maintenance of sound transduction and auditory neurotransmission with noise and ageing

Prominent physiological mechanisms that sustain cochlear function across a lifetime in the face of noise stress are highlighted. Central to this are humoral and intracellular processes protecting the mechanotransducer apparatus, and sustaining neurotransmission across the cochlear hair cell spiral ganglion afferent synapse. At the level of the cochlear partition, 'purinergic hearing adaptation' desensitises cochlear hair cell - mediated sound transduction, protecting the hair cells and their afferent synapses from sustained noise stress. Within hair cells, Ca2+ buffering and active extrusion are central to mechanotransducer function and control of glutamatergic neurotransmission. With acoustic hyperstimulation plasticity in pre-synaptic and post-synaptic specialisations, particularly structural and molecular responses of ribbon complexes likely mitigate synaptopathy.