蜗轴切除术后囊泡膜谷氨酸转运体阳性终末在豚鼠耳蜗核内的变化

Changes of vesicular glutamate transporter positive terminals in guinea pig cochlear nucleus after unilateral cochlear axis ablation

目的研究豚鼠行单侧蜗轴切除术后双侧蜗神经核复合体内囊泡膜谷氨酸转运体(vesicular glutamate transporter,VGluTs)表达的变化情况,以明确VGluTs阳性终末在第一级听觉中枢中的分布情况及功能。方法将正常成年豚鼠行单侧内耳蜗轴切除术,手术前、后行听觉脑干诱发电位(ABR)检测,术后1周应用免疫组织化学染色ABC法观察双侧脑干蜗神经核内VGluTs阳性终末的分布及变化情况。结果正常豚鼠蜗神经前腹侧核、后腹侧核、背侧核内均可见丰富的VGluT1阳性终末分布,腹侧核内可见阳性终末环绕神经元胞体形成密切接触。VGluT2阳性终末主要分布于蜗神经背侧核中间层及腹侧核边缘小细胞壳区。豚鼠单侧蜗轴切除术后一周,手术同侧蜗神经腹侧核内VGluT1阳性终末几乎全部消失,与对侧及对照组蜗神经腹侧核对比鲜明。蜗神经核内VGluT2阳性终末在蜗轴切除术后一周未发现明显变化。结论蜗神经腹侧核内大量的Ⅰ型囊泡膜谷氨酸转运体(VGluT1)阳性终末起源于同侧耳蜗螺旋神经节;VGluT1是研究初级听觉传入通路中谷氨酸能神经元终末的良好标志;VGluT1和VGluT2在听觉传导系统及听觉中枢中的分布有差异,提示了功能上的不同。

Objective To investigate the disposition and functions of vesicular glutamate transporter （VGluT） positive terminals in guinea pig cochlear nucleus. Methods Unilateral surgical ablation of the cochlear axis was carried out in adult guinea pigs. Auditory brainstem responses were tested before and after the surgery. One week after the surgery, location of VGluT positive terminals in the cochlear nucleus was examined bilaterally with immunohistoehemieal techniques. Results In normal animals, large amounts of VGluTl-immunoreaetive （VGluT1-LI） terminals were visible in the anteroventral cochlear nucleus （AVCN）, posterior ventral cochlear nucleus （PVCN） and dorsal cochlear nucleus （DCN）, surrounding neurons and forming efose contacts in the ventral cochlear nucleus （VCN）. GluT2-immunoreaetive （VGluT2-LI） terminals were principally found in the middle layer in DCN and in the small cell shell （SCS） region. One week after unilateral cochlear axis ablation, VGluT1-LI terminals disappeared in the ipsilateral AVCN almost entirely, in vivid contrast with the opposite side and control group. Changes of VGluT2-LI terminals in the cochlear nucleus were not obvious one week after unilateral cochlear axis ablation. Conclusion VGluT1-LI terminals in the VCN appear to originate from the ipsilateral spiral ganglion. VGluTI are markers of glutamatergie axon terminals useful in studying the primary auditory afferent system; The different distribution of VGluTI and VGluT2 indicate that they have different functions in the auditory transmitting system and auditory centers.