Abstract
Two neurotrophins and their high affinity tyrosine kinase receptors mediate neuronal survival and fiber guidance in the developing ear. Neurotrophins are also essential for adult sensory survival. New models based on other tyrosine kinase receptor treatments may help maintain inner ear innervation beyond the apparently inevitable loss of hair cells with age, one major source of neurotrophins in the adult ear, and may improve prospects to treat hearing loss.