Scates K W, Woods C I, Azeredo W J
Department of Otolaryngology and Communication Sciences, SUNY Health Science Center at Syracuse, NY 13210, USA.
Hear Res. 1999 Feb;128(1-2):51-60. doi: 10.1016/s0378-5955(98)00198-1.
The external, central and dorsal subnuclei of the inferior colliculus (ICX, ICC, ICD respectively) have different patterns of descending projections to the periolivary region. We found that electrical stimulation of these subnuclei in anesthetized rats causes suppression of 2f1-f2 distortion product otoacoustic emissions (DPOAE). The responses in DPOAEs to stimulation of ICX and ICC are characterized by a large (7-25 dB), initial suppression which lasted 25-30 s (early phase) followed by a sustained smaller (3-15 dB) suppression (late phase). ICX stimulation produces the largest suppressions of DPOAEs in both contralateral and ipsilateral ears equally. Stimulation of the ICC causes large suppressions in the contralateral ear DPOAEs but much smaller than the suppressions of DPOAEs caused by ICX stimulation. Stimulation of the ICC causes a much smaller suppression in the ipsilateral ear DPOAEs than in the contralateral ear DPOAEs. ICD stimulation, however, produces little or no suppression of DPOAEs in either ear when compared to other subnuclei. No frequency-specific changes in DPOAEs were seen with stimulation of any of the subnuclei of the inferior colliculus (IC). Sectioning of middle ear muscles did not negate the suppressive effects of IC stimulation on DPOAEs. These findings verify that the IC has a subnucleus-specific influence over cochlear micromechanics.
下丘的外侧、中央和背侧亚核（分别为ICX、ICC、ICD）对橄榄周区域有不同的下行投射模式。我们发现，在麻醉大鼠中电刺激这些亚核会导致2f1-f2畸变产物耳声发射（DPOAE）受到抑制。DPOAE对ICX和ICC刺激的反应特征是，最初有较大幅度（7 - 25 dB）的抑制，持续25 - 30秒（早期阶段），随后是持续较小幅度（3 - 15 dB）的抑制（晚期阶段）。ICX刺激在对侧耳和同侧耳中对DPOAE产生的抑制作用同样最大。刺激ICC会使对侧耳DPOAE受到较大抑制，但远小于ICX刺激引起的DPOAE抑制。刺激ICC对同侧耳DPOAE的抑制比对侧耳DPOAE的抑制小得多。然而，与其他亚核相比，ICD刺激在任一耳中对DPOAE几乎没有或没有抑制作用。刺激下丘（IC）的任何亚核，DPOAE均未出现频率特异性变化。切断中耳肌肉并未消除IC刺激对DPOAE的抑制作用。这些发现证实，IC对耳蜗微力学具有亚核特异性影响。
