TY - JOUR
T1 - Distortion-product emissions in rabbit
T2 - I. Altered susceptibility to repeated pure-tone exposures
AU - Mensh, Brett D.
AU - Patterson, Matthew C.
AU - Whitehead, Martin L.
AU - Lonsbury-Martin, Brenda L.
AU - Martin, Glen K.
N1 - Funding Information:
Portions of this researchw ere supportedb y grants from the Public Health Service (DC00313,D CO0613, ES03500,N S071821a, nd the DeafnessR esearchF oun-dation. This report is based on a thesis submittedt o Baylor College of Medicine by B.D. Mensh in partial
PY - 1993/10
Y1 - 1993/10
N2 - An important issue in understanding the development of noise-induced hearing loss is whether prior acoustic overstimulation alters the susceptibility of the cochlea to further damage. The present work was designed to establish a model of activity-dependent changes in the susceptibility of the cochlea to acoustic overstimulation by regularly exposing the ear to a low-frequency pure tone. As a quantitative index of cochlear function, 2f{hook}1-f{hook}2 distortion-product otoacoustic emissions (DPOAEs) were monitored systematically over time in three groups of rabbits, with each group experiencing a unique paradigm that incorporated repeated exposure to the low-frequency tone. Common to each rabbit's exposure protocol was that a given experimental session consisted of two exposure episodes, separated by a 40-min period. Experimental sessions were repeated three times, with 2- to 3-day recovery periods interposed between sessions. The rate of decrement in DPOAE amplitude over a prescribed time period was utilized as a measure of susceptibility to the acoustic trauma. The overall results indicated that ears were more susceptible to exposure 40 mins after the first exposure of a session than they were initially. A series of control experiments indicated that the robustness of the acoustic middle-ear reflex (AMR) did not change between the exposure episodes. Consequently, changes in the AMR could not account for the increased susceptibility seen following the first exposure. However, in awake rabbits with stronger AMRs, higher pure-tone exposure levels were needed to produce increased susceptibility to the second exposure. After 2-3 days of intersession recovery, susceptibility to the effects of excessive sound returned close to its original baseline level. The outcome of these studies demonstrated a reduced capacity for the ear to resist the harmful effects of exposure to a moderately intense tone, which was repeated twice over a brief 40-min period, but little change in susceptibility when identical exposures were repeated over longer intersession intervals of several days.
AB - An important issue in understanding the development of noise-induced hearing loss is whether prior acoustic overstimulation alters the susceptibility of the cochlea to further damage. The present work was designed to establish a model of activity-dependent changes in the susceptibility of the cochlea to acoustic overstimulation by regularly exposing the ear to a low-frequency pure tone. As a quantitative index of cochlear function, 2f{hook}1-f{hook}2 distortion-product otoacoustic emissions (DPOAEs) were monitored systematically over time in three groups of rabbits, with each group experiencing a unique paradigm that incorporated repeated exposure to the low-frequency tone. Common to each rabbit's exposure protocol was that a given experimental session consisted of two exposure episodes, separated by a 40-min period. Experimental sessions were repeated three times, with 2- to 3-day recovery periods interposed between sessions. The rate of decrement in DPOAE amplitude over a prescribed time period was utilized as a measure of susceptibility to the acoustic trauma. The overall results indicated that ears were more susceptible to exposure 40 mins after the first exposure of a session than they were initially. A series of control experiments indicated that the robustness of the acoustic middle-ear reflex (AMR) did not change between the exposure episodes. Consequently, changes in the AMR could not account for the increased susceptibility seen following the first exposure. However, in awake rabbits with stronger AMRs, higher pure-tone exposure levels were needed to produce increased susceptibility to the second exposure. After 2-3 days of intersession recovery, susceptibility to the effects of excessive sound returned close to its original baseline level. The outcome of these studies demonstrated a reduced capacity for the ear to resist the harmful effects of exposure to a moderately intense tone, which was repeated twice over a brief 40-min period, but little change in susceptibility when identical exposures were repeated over longer intersession intervals of several days.
KW - 2f{hook}-f{hook} distortion-product emissions
KW - Acoustic middle-ear reflex
KW - Pure-tone exposure
KW - Rabbit
KW - Resistance
KW - Susceptibility
KW - Temporary-threshold shift
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U2 - 10.1016/0378-5955(93)90051-2
DO - 10.1016/0378-5955(93)90051-2
M3 - Article
C2 - 8276732
SN - 0378-5955
VL - 70
SP - 50
EP - 64
JO - Hearing Research
JF - Hearing Research
IS - 1
ER -