豚鼠畸变产物耳声发射潜伏期的对侧抑制效应现象

目的 通过观察对侧抑制效应中畸变产物耳发射（distortion productotoacousticemissions,DPOAE)各指标的改变，探讨耳蜗生理机制及传出神经的调节机能。方法 12只健康杂色豚鼠分A、B2组，在对侧耳无声刺激及给予70dB SPL宽带噪声条件下，分别使用不同的原始纯音强度组合测定在f2＝2、4、6kHz时测试耳DPOAE之幅值及潜伏期。次日，A组动物背侧径路开放右耳听泡，圆窗膜给予60mmol/L卡因酸1μL，作用3h后拭去。给药后6h测试右耳无声刺激和给予70dB SPL宽带噪声刺激下，左耳的DPOAE幅值、潜伏期等指标。结果 ①用药前，A组对侧耳给声时以等强度原始音诱发的测试耳DPOAE各频率幅值与给声前基本无变化，而潜伏期显著延长；②用药前，B组对侧耳给声以差强度原始音（L2＝L1－10dB)诱发的测试耳DPOAE在2、4kHz的幅值与给声前相比有显著减小，潜伏期也显著延长；③A组用药后，对侧耳给声对测试耳DPOAE幅值和潜伏期均无显著影响。结论 潜伏期亦是对侧抑制研究中的敏感指标。对侧抑制效应在调制耳蜗转导机制中发挥负反馈作用。

Contralateral suppression of latency during distortion product otoacoustic emissions detection in guinea pigs]

OBJECTIVE: To investigate the cochlear micromechanics and the function of cochlear efferent system by detecting the distortion product otoacoustic emissions (DPOAE) with or without contralateral acoustic stimulation. METHODS: The DPOAE amplitude and latency of the cubic DPOAE (2f1-f2) were measured at f2 = 2, 4 and 6 kHz with or without 70 dB SPL broad-band noise contralateral stimulation in ears of 12 healthy pigmented guinea pigs, which were divided into two groups(A and B) and tested with different primary intensity level combinations. On the next day, an operation was made to open the acoustic bulla of right ear in Group A. Kainic Acid (KA, 1 microL of 60 mmol/L) was applied onto the round window membrane and wiped up carefully after three hours. The amplitude and latency of the cubic DPOAE from the left ear were measured after 6 hours of KA administration, with or without contralateral noise stimulation. RESULTS: Before the KA treatment, the amplitude of DPOAE induced by primaries of equal levels (L1 = L2) presented no significant change and the latency prolonged significantly during contralateral acoustic stimulation (Group A). But the amplitude at 2, 4 kHz of DPOAE induced by primaries of different levels (L1 > L2) decreased significantly and the latency also prolonged significantly (Group B). After KA administration in the contralateral ear of Group A, the contralateral acoustic stimulation had no significant effect on either amplitude or latency of DPOAE measured ipsilaterally. CONCLUSION: The result demonstrates that the latency is a sensitive index for the cochlear contralateral suppression. The efferent system may act as a negative feedback during the cochlear transduction.