The Suppressive Effect of the Olivocochlear Bundle in Rats Studied by Brainstem Auditory Evoked Potentials Following Brainstem Lesion

以腦幹聽覺誘發電位探討大鼠腦幹受損後對其橄欖耳蝸神經束抑制功能之影響

謝悅齡(Yueh-Ling Hsieh) ； 陳順勝(Shun-Sheng Chen) ； 陳贊如(Tsan-Ju Chen)

《The Kaohsiung Journal of Medical Sciences》 14卷11期 (1998/11) Pp. 679-690

https://doi.org/10.6452/KJMS.199811.0679

摘要

橄欖耳蝸神經束，簡稱為OCB，起源於腦幹的上橄欖核體，再投射到同側及對側的耳蝸中。經多文獻顯示OCB會抑制聽神經的活動，而對內耳產生保護作用。本研究採用較便利的輻射頻率凝結法破壞大鼠OCB後，評估OCB功能受影響的情形。共有30隻Wistar雄鼠分成四維，除對照組外，另外三組分別進行左側、右側及中央三個不同部位OCB之破壞。接莽再著由腦幹聽覺誘發電位(BAEP)的記錄，評估OCB受損後，上行聽覺徑路傳導之變化。結果顯示，對照組大鼠的BAEP，波振幅及波潛時均無顯著改變。然而，在OCB破壞後，BAEOP波潛時無顯著變化，但第I至III波的波振幅則有顯著的增加。此乃因破壞OCB後，造成去抑制作用，進而使得聽覺傳導徑路上的聽神經、耳蝸神經核及上橄欖核體的神經性活動增加，因而使BAEP波振幅增大。當破壞單側OCB時，會造成同側BAEP的波振幅增加，而破壞中央處的OCB時，則兩側BAEP的波振幅均顯著增加。著由這些結果證實：(1) 破壞OCB會造成對上行聽覺徑路傳導的去抑制，而使BAEP某些波形的波振幅增加；(2)記錄BAEP對評估OCB功能是一方便且有效方法。

並列摘要

The olivocochlear bundle (OCB) stems from the superior olivary complex in the brainstem and projects to the ipsilateral and contralateral cochlea. Several studies have suggested that the OCB has a suppressive effect on the inner ear by inhibiting the responses of the primary afferent fibers. To evaluate the action of OCB by more available measurement, radiofrequency lesion was applied to 30 Wistar rats which were divided into four groups, a sham group and another three groups with different OCB lesion sites. Consequent changes following OCB lesion were evaluated by measuring the brainstem auditory evoked potentials (BAEPs), which are considered to reflect the auditory brainstem afferent conduction. The amplitudes and latencies did not change significantly after sham treatment. However, although the BAEP peak latencies were not significantly altered after damaging the OCB, the amplitudes of the BAEP waves I to III were augmented significantly. These results indicate that increased neural activities were presented in the auditory nerves, cochlear nucleus and the superior olivary complex upon disinhibition of the OCB. Unilateral OCB lesions predominantly augmented BAEP waqveform which was recorded ipsilaterally to the lesion side. Upon lesion of the midline OCB, BAEP recordings on either side showed significant increments in the amplitudes of waves I to III. These findings are compatible with those observed in the cat model and other rodents, and thus confirm that (1) OCB lesion leads to increased amplitudes in some BAEP peaks which were evoked by certain hyperactive auditory nuclei and tracts; and (2) BAEP measurement is a convenient and useful tool for assessing the OCB function.

並列關鍵字

olivocochlear bundle ； suppressive effect ； brainstem auditory evoked potentials