Effect of Temperature on the Transient Evoked and Distortion Product Otoacoustic Emissions in RatsKhvoles R. · Freeman S. · Sohmer H.
Department of Physiology, Hebrew University, Hadassah Medical School, Jerusalem, Israel
In order to study the energy dependence of the cochlear amplifier, transient evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) were recorded in rats during gradual cooling to 27°C and heating to 40°C. In the range 33–39°C, the TEOAEs and DPOAEs were maximal in amplitude and almost insensitive to temperature. However, they were significantly depressed (reversibly) at higher and lower temperatures. Intensity functions were plotted at 37, 27 and 40°C for both types of oto-acoustic emissions. At 37°C intensity functions were nonlinear, with a notch at mid-intensity regions. At 27°C, the magnitudes were depressed more at the lower intensities and threshold elevations were observed. As a result, the intensity functions were more linear and the notch was no longer seen. This result provides further evidence for a more active, energy-dependent component of the otoacoustic emissions at lower intensities for both TEOAEs and DPOAEs. The cooling probably affects the lower intensity otoacoustic emissions by inducing a depression in the endocochlear potential, by reducing the motility of the outer hair cells and by introducing a small conductive hearing loss.
Prof. H. Sohmer, Department of Physiology
Hebrew University, Hadassah Medical School, POB 12272
Jerusalem 91120 (Israel)
Tel. +972 2 6758385, Fax +972 2 6439736
Part of a PhD thesis to be submitted by R.K. to the Senate of the Hebrew University.
Received: Received: April 28, 1997
Accepted after revision: April 29, 1998
Number of Print Pages : 12
Number of Figures : 6, Number of Tables : 0, Number of References : 33
Audiology & Neuro-Otology (Basic Research and Clinical Applications)
Vol. 3, No. 6, Year 1998 (Cover Date: November-December 1998)
Journal Editor: Manfried Hoke, Münster, Germany
ISSN: 1420–3030 (print), 1421–9700 (Online)
For additional information: http://www.karger.com/journals/aud.htm