Age-related hearing loss in the Fischer 344/NHsd rat substrain.
Studies of the F344 rat have shown a variety of age-related auditory anatomy and physiology changes. The current study was undertaken to clarify the ARHL in the F344 rat, by examining the auditory pathway of the F344/NHsd substrain that is distributed by Harlan Laboratories for research in the United States. The F344/NHsd rat begins to lose its hearing at about 12 months, and by 24 months, there are 50-60 dB auditory brainstem response threshold shifts at 20 and 40 kHz and 20 dB losses at 5-10 kHz. Distortion product otoacoustic emissions (DPOAE) amplitudes at 1.8-12 kHz stimuli were depressed in the older (18-24 months) rats. Amplitude input-output functions of the compound action potential (CAP) were also depressed across frequency. The endocochlear potential (EP) was 90-100 mV in the 3 month old rats. All but one of the 24 month old rats' EPs were in the +75-85 mV range. Tympanometry revealed no differences in middle ear function between the young and older rats. Collectively, these findings suggest damage to the outer hair cells, but anatomical examination of the outer hair cells revealed a relative lack of cell loss compared to the magnitude of the hearing and DPOAE loss.
Center for Hearing and Deafness, Department of Communicative Disorders and Sciences, State University of New York at Buffalo, 137 Cary Hall, 3435 Main Street, Buffalo, NY 14214, United States. ecb2@buffalo.edu
Eric C
EC
Bielefeld
Donald
D
Coling
Guang-Di
GD
Chen
Manna
M
Li
Chiemi
C
Tanaka
Bo-Hua
BH
Hu
Donald
D
Henderson
D000158:Acoustic Impedance Tests; D000161:Acoustic Stimulation; D000367:Age Factors; D000375:Aging; D000818:Animals; D001306:Auditory Pathways / Q000473:pathology / Q000503:physiopathology*; D001309:Auditory Threshold; D003051:Cochlea / Q000503:physiopathology; D003056:Cochlear Nerve / Q000503:physiopathology; D016057:Evoked Potentials, Auditory, Brain Stem; D018072:Hair Cells, Auditory, Outer / Q000473:pathology; D034381:Hearing Loss / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous; D051381:Rats; D011916:Rats, Inbred F344; D013045:Species Specificity