title: Auditory thresholds in rats of different age and strain. A behavioral and electrophysiological study.
abstract: The auditory sensitivity of albino rats was determined behaviorally by conditioned suppression of licking and electrophysiologically by the auditory brain stem response (ABR). The behavioral thresholds were obtained with 10-Hz frequency-modulated tones, and the ABR with 1/1- or 1/3-octave filtered sine waves. Individual variability, reproducibility of responses and the influence of sex, age and strain were investigated. The behavioral and electrophysiological techniques were compared in animals with noise-induced high-frequency hearing losses. The results showed the highest degree of normal auditory sensitivity to be around 12-24 kHz. The variability in 20 rats was about 15 dB. In young animals, strain and sex had no influence. A deterioration in high-frequency hearing sensitivity was observed in aged hypertensive rats, whereas normotensive ones showed only minimal changes. The thresholds obtained with the electrophysiological (ABR) technique were 10-20 dB higher than those obtained behaviorally. Both techniques (behavioral and 1/3-octave ABR) assess high-frequency hearing loss equally well. It was concluded that the ABR (1/3-octave filtered sine waves) is suitable for the determination of hearing thresholds and the assessment of hearing loss, at least in the high-frequency range. The ABR technique is especially useful in long-term experiments during which thresholds are determined repeatedly.
mesh_terms: D000367:Age Factors; D000375:Aging; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology*; D004597:Electroshock; D005072:Evoked Potentials, Auditory; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000503:physiopathology; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D011571:Psychoacoustics; D051381:Rats; D011919:Rats, Inbred Strains / Q000235:genetics / Q000502:physiology*; D012737:Sex Factors; D013045:Species Specificity