Sensitivity of unanesthetized chinchilla auditory system to noise burst onset, and the effects of carboplatin

• Published in: Hearing research Vol. 155; no. 1; pp. 133 - 142
• Main Authors: Phillips, D.P., Hall, S.E., Guo, Y., Burkard, R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-05-2001; Elsevier
• Subjects: Acoustic Stimulation; Animals; Antineoplastic Agents - toxicity; Auditory nerve; Biological and medical sciences; Carboplatin; Carboplatin - toxicity; Chinchilla; Cochlear Nerve - drug effects; Cochlear Nerve - physiology; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Electrophysiology; Evoked Potentials, Auditory - drug effects; Evoked response; Fundamental and applied biological sciences. Psychology; Inferior Colliculi - drug effects; Inferior Colliculi - physiology; Inferior colliculus; Noise; Noise onset; Vertebrates: nervous system and sense organs; IC, inferior colliculus; Noise onset; Inferior colliculus; OHC, outer hair cell; AN, auditory nerve; Evoked response; Auditory nerve; SDH, succinate dehydrogenase; ICP, inferior colliculus potential; CAP, compound action potential; SPL, sound pressure level; PL, plateau level; IHC, inner hair cell; Carboplatin; Noise; Rodentia; Central nervous system; Discharge pattern; Electrophysiology; Outer hair cell; Chinchilla; Vertebrata; Sensitivity; Mammalia; Acoustic stimulus; Colliculus inferior; Inner hair cell; Auditory pathway; Brain (vertebrata)
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/S0378-5955(01)00249-0

The gross near-field responses of the auditory nerve and inferior colliculus to noise burst stimuli were recorded through intracranially implanted electrodes in six unanesthetized chinchillas. Responses were studied as a function of stimulus plateau amplitude and rise time, both before and after a systemic dose of 75 mg/kg of carboplatin. Both recording sites showed sensitivity to stimulus level and rise time. Increases in stimulus level and decreases in stimulus rise time each produced increases in the response magnitude, and decreases in response latency. When the stimuli were re-specified as rate of pressure change at sound onset (Pa/s), the amplitude and latency of responses at each site were found to be a direct function of rate of sound pressure change. These data provide the first confirmation in unanesthetized animals of previous single unit observations in barbiturate-anesthetized cats. Carboplatin treatment resulted in a 20–80% loss of inner hair cells, a modest threshold elevation, and a 50–75% reduction in peak response amplitudes. The general patterns of sensitivity to stimulus level and rise time were not markedly affected by carboplatin, nor was the fashion in which response parameters (amplitude and latency) were ruled by rate of pressure change at sound onset.