Ison James R, Allen Paul D
Department of Brain and Cognitive Sciences, Meliora Hall, University of Rochester, Rochester, NY 14627, USA.
J Assoc Res Otolaryngol. 2003 Dec;4(4):495-504. doi: 10.1007/s10162-002-3046-2. Epub 2003 Jun 6.
The strength of the acoustic startle reflex (ASR) as a function of age was studied in adult C57BL/6J and CBA/CaJ mice, because altered ASR levels are a potential behavioral consequence of the neural reorganization that accompanies the early-onset hearing loss of the C57BL, in contrast to the normal-hearing CBA. For C57BL mice at 14-36 weeks of age, compared with 7-week-old mice, high-frequency thresholds measured with the auditory brainstem response (ABR) were less sensitive by about 25-30 dB while the hearing loss at low frequencies was 10-15 dB, but by 60 weeks losses of 45-50 dB were present across the entire spectrum. Their ASR amplitudes for 16 kHz tone pips were highest at 7 weeks and then declined with age, but, for 4 kHz tones the ASR increased in strength at 18 weeks and beyond to levels above that of the younger mice. This hyperreactivity persisted even in 60-week-old mice. The ASR for 16 kHz stimuli was positively correlated with hearing sensitivity, but the ASR for 4 kHz stimuli was positively correlated with hearing loss for mice that were 18-36 weeks of age. Furthermore, ASR amplitudes for 4 kHz stimuli were positively correlated with the 16 kHz ASR in young C57BL mice but negatively correlated in older mice. There were no similar ASR or ABR changes in adult CBA mice through 19 weeks of age. Correlations between ASR and ABR scores were always weakly positive, and correlations between 4 kHz and 16 kHz ASR amplitudes were always strongly positive. The ASR data in older C57BL mice with hearing loss are consistent with reports describing their increased neural representation of low-frequency sounds and reinforce the value of this strain for studying the functional consequences that accompany age-related cochlear degeneration.
研究了成年C57BL/6J和CBA/CaJ小鼠的听觉惊吓反射（ASR）强度随年龄的变化，因为与听力正常的CBA小鼠相比，ASR水平的改变是C57BL早期听力丧失所伴随的神经重组的一种潜在行为后果。对于14至36周龄的C57BL小鼠，与7周龄小鼠相比，用听觉脑干反应（ABR）测量的高频阈值敏感度降低了约25至30 dB，而低频听力损失为10至15 dB，但到60周时，整个频谱的听力损失达到45至50 dB。它们对16 kHz短纯音的ASR幅度在7周时最高，然后随年龄下降，但对于4 kHz音调，ASR强度在18周及以后增加到高于年轻小鼠的水平。这种反应过度甚至在60周龄的小鼠中也持续存在。对于18至36周龄的小鼠，16 kHz刺激的ASR与听力敏感度呈正相关，但4 kHz刺激的ASR与听力损失呈正相关。此外，年轻C57BL小鼠中4 kHz刺激的ASR幅度与16 kHz ASR呈正相关，而老年小鼠中呈负相关。19周龄以内的成年CBA小鼠没有类似的ASR或ABR变化。ASR和ABR分数之间的相关性总是呈弱正相关，4 kHz和16 kHz ASR幅度之间的相关性总是呈强正相关。老年听力损失的C57BL小鼠的ASR数据与描述其低频声音神经表征增加的报告一致，并强化了该品系在研究与年龄相关的耳蜗退化所伴随的功能后果方面的价值。
