The effects of experimentally increased perilymphatic pressure on click-evoked otoacoustic emissions in guinea pigs.
We used the IL088 Otodynamic Analyzer system to study click-evoked otoacoustic emissions (CEOAEs) in 30 healthy guinea pigs. The animals were anesthetized and patterns of the CEOAEs were evaluated before manipution, after the tympanic bulla was opened, and after formation of a microfistula on the basal turn of the cochlea. The animals then were divided into three pressure loading groups (10, 20, and 30 cm H2O). CEOAEs were recorded with a capillary manometer at pretest, 5, 10, 20, 30, 45, and 60 min after perilymphatic pressure loading to the basal turn of cochlea, and 10 and 20 min after pressure unloading. As perilymphatic pressure increased, all three pressure groups showed maximum decreases in both echo response and reproducibility 5 min after pressure loading. In the 10 cm H2O pressure group, emissions recovered 10 min after pressure loading, and this tendency continued. However, in the 20 and 30 cm H2O pressure groups, no recovery of emissions was seen throughout the 60 min observation period, except for emissions after pressure unloading. The results suggest that the echo response and reproducibility may be sensitive indicators of cochlear function and perilymphatic pressure regulation capacity.
Chang
S O
SO
Department of Otorhinolaryngology, College of Medicine, Seoul National University, Korea.
Noh
K T
KT
Min
Y G
YG
Yu
W S
WS
Lee
D W
DW
D000161:Acoustic Stimulation; D000818:Animals; D003051:Cochlea / Q000502:physiology*; D006168:Guinea Pigs; D010498:Perilymph / Q000502:physiology*