Morphological and Physiological Studies for Age-Related Change in Gerbil's Cochlear Nucleus
Grant-in-Aid for Scientific Research (B).
|Research Institution||Kanazawa Medical University|
EDAMATSU Hideo KANAZAWA MEDICAL UNIVERSITY,ASSOCIATE PROFESSOR, 医学部, 助教授 (50151981)
横山 和則 東京医科歯科大学, 耳鼻科, 助手 (90220566)
MATSUHIRA Toshimasa KANAZAWA MEDICAL UNIVERSITY,INSTRUCTOR, 医学部, 講師 (50131032)
安田 誠夫 金沢医科大学, 耳鼻科, 講師 (70239763)
小川 明 自衛隊中央病院, 耳鼻科, 部長 (40107280)
高野 正美 金沢医科大学, 耳鼻科, 講師 (60187987)
MIYAUTI Hiroshi KANAZAWA MEDICAL UNIVERSITY,INSTRUCTOR, 医学部, 講師 (10247455)
|Project Fiscal Year
1991 – 1993
Completed(Fiscal Year 1993)
|Budget Amount *help
¥3,900,000 (Direct Cost : ¥3,900,000)
Fiscal Year 1993 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1992 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1991 : ¥1,800,000 (Direct Cost : ¥1,800,000)
|Keywords||GERBIL / AGING / AUDITORY FUNCTION / ABR / COCHLEAR NUCLEUS / NEURAL DEGENERATION / Gerbil / Aging / Auditory function / Cochlear nucleus / Neural degeneration / Vacuolation / Presbycusis / Auditory brainstem response / Cochlear microphonics / vacuole|
A degenerative lesion of the auditory system of mongolian gerbil (Meriones unguiculatus) was reported by K.Morest et al., 1986. The lesion was evaculation confined to the cochlear nucleus (CN) and increased with age. This study was performed to explore an effect of age-related lesion in gerbil's CN on the auditory function. 30 gerbils from 21 days to 2 years and 3 months old were used. They have had no ear infection. The auditory function was electrophysiologically evaluated by recording of cochlear microphonics (CM) and auditory brain stem response (ABR). Then CN and cochlea were microscopically observed. Correlation of the occurrence of lesion was examined with change of CM and ABr.
Evaculation in gerbil's CN began to appear at around 7 weeks of age and the lesion increased in number and size with age. Number of vacuoles in average was less than 5 for 7-week-old gerbils and more than 15 for over 4-month-old gerbils. Mean size of each vacuole was smaller than 50 mum^2 for the former ge
rbils and became larger than 150 mum^2 for the latter. Unlikely with the age-related changes in the cochlear nucleus, no vacuole was seen in cochlea. CM thresholds of gerbils at the frequency range of 1 k - 8kHz increased with aging. The CM thresholds of 4-month-old gerbil were 20-30 dB lower than those of the over 2-year-old gerbils. Similarly with the change of CM thresholds, ABR thresholds increased 15-20 dB with their age. Latencies of ABR waves became elongated along with the increased thresholds. Inter-wave latencies between I and V were also more prolonged in over 2-year-old gerbils than in the younger gerbils. However this delay was almost same with the prolongation of latencies which was caused by the increased thresholds of ABR.
The results of CM and ABR in this study showed that auditory function in the cochlea and brain stem pathway of gerbils reached adult levels at about 4 months of age and gradually decreased with age. So far we have not found the direct effect of lesions in the CN on the age-related auditory function of gerbils.
Research Output (14results)