title: Insensitivity of the audiogram to carboplatin induced inner hair cell loss in chinchillas.
abstract: Noise trauma, aging, and ototoxicity preferentially damage the outer hair cells of the inner ear, leading to increased hearing thresholds and poorer frequency resolution. Whereas outer hair cells make synaptic connections with less than 10% of afferent auditory nerve fibers (type-II), inner hair cells make connections with over 90% of afferents (type-I). Despite these extensive connections, little is known about how selective inner hair cell loss impacts hearing. In chinchillas, moderate to high doses of the anticancer compound carboplatin produce selective inner hair cell and type-I afferent loss with little to no effect on outer hair cells. To determine the effects of carboplatin-induced inner hair cell loss on the most widely used clinical measure of hearing, the audiogram, pure-tone thresholds were determined behaviorally before and after 75 mg/kg carboplatin. Following carboplatin treatment, small effects on audiometric thresholds were observed even with extensive inner hair cell losses that exceed 80%. These results suggest that conventional audiometry is insensitive to inner hair cell loss and that only small populations of inner hair cells appear to be necessary for detecting tonal stimuli in a quiet background.
authors.affiliation: University of Florida, Department of Speech, Language, and Hearing Sciences, Gainesville, FL, USA. elobarinas@ufl.edu
authors.forename: Edward
authors.initials: E
authors.lastname: Lobarinas
authors.forename: Richard
authors.initials: R
authors.lastname: Salvi
authors.forename: Dalian
authors.initials: D
authors.lastname: Ding
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000187:drug effects / Q000502:physiology; D016190:Carboplatin / Q000009:adverse effects*; D002682:Chinchilla; D003051:Cochlea / Q000187:drug effects / Q000473:pathology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects*; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects; D006309:Hearing / Q000502:physiology; D008297:Male; D011601:Psychophysics; D011984:Sensory Receptor Cells / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D016190:Carboplatin