大鼠单侧耳蜗毁损后脑干听觉中枢谷氨酸脱羧酶的表达

目的:研究大鼠单侧耳蜗毁损后脑干听觉中枢(耳蜗核及下丘)谷氨酸脱羧酶(GAD65)水平在术后不同时间点的变化,探讨大鼠脑干听觉中枢在去传入损伤后功能重组的去抑制过程。方法:采用免疫组织化学方法,通过计算机图像分析系统分别检测大鼠单侧耳蜗毁损后第3,7,30天耳蜗核及下丘GAD65的含量水平。结果:单侧耳蜗毁损后3天手术同侧耳蜗核及双侧下丘GAD65含量水平较正常对照组显著性下降。手术后第7天,手术同侧耳蜗核及双侧下丘GAD65水平均有轻度回升,但仍显著低于正常对照组。手术后第30天,GAD65水平基本恢复到正常水平。手术对侧下丘GAD65水平的下降程度显著低于手术同侧,手术对侧耳蜗核GAD65水平在术后无显著变化。结论:耳蜗去传入损伤后,脑干听觉中枢GAD65含量呈现一明显的动态变化过程,提示听觉中枢可能通过D-氨基丁酸(GABA)合成的减少而产生去抑制,从而发生功能重组。

GAD Levels in the Auditory Brainstem of the Rat Following Unilateral Cochleotomy

Objective: To explore the disinhibition processes of the central auditory system following the unilateral deafferentation.Methods: The levels of glutamic acid decarboxylase(GAD,the synthesizing enzyme for GABA) in the adult rat cochlear nucleus(CN) and inferior colliculus(IC) at varying times after cochlear ablation were assayed using the imaging system software.Results: There was a significant decrease in GAD_(65) immunoreactivity in the ipsilateral(left) cochlear nucleus and bilateral inferior colliculus(IC) at 3 and 7 d after the left cochlear ablation than that found in the bilaterally intact control animals,with complete recovery 30 days postoperation. Levels of GAD_(65) in the ipsilateral IC were significant less than in the contralateral IC.In contrast,no significant modification of GAD in the contralateral cochlear nucleus had been shown at post-ablation survival periods examined.Conclusion: The results presented here suggest that inhibitory processes in the central auditory system are rapidly modified after unilateral deafening,followed by a reduction of inhibitory neurotransmitter synthesis.