γ-氨基丁酸能抑制可锐化大棕蝠听皮层神经元频率调谐  

GABAERGIC INHIBITION CAN SHARPEN FREQUENCY TUNING OF AUDITORY CORTICAL NEURONS IN BIG BROWN BAT (EPTESICUS FUSCUS)

作　　者：陈其才[1] P.H.-S.JEN 吴飞健 

机构地区：[1]华中师范大学生物学系,武汉430079 [2]密苏里大学生物科学系

出　　处：《动物学报》2002年第3期346-352,共7页ACTA ZOOLOGICA SINICA

基　　金：国家自然科学基金资助项目 (No 39740 0 0 2 );国家教育部科技基金资助项目 (No 96 14 6 );美国NSF基金资助项目~~

摘　　要：本实验使用了 9只成年健康的大棕蝠 (Eptesicusfuscus)。采用双声刺激和多管电极电泳导入荷包牡丹碱 (bicuculline,Bic)的方法 ,研究了γ 氨基丁酸 (γ aminobutyricacid ,GABA)能抑制在锐化听皮层 (primaryauditorycortex ,AC ,即初级听皮层 )神经元频率调谐中的作用。结果发现 :正常AC神经元的频率调谐曲线表现出单峰开放式、多峰开放式和单峰封闭式 3种类型 ;用双声刺激方法研究证实 ,至AC神经元的抑制性输入能被抑制性声刺激所激活 ,且这种神经抑制有自身的最佳频率 ,根据其对兴奋反应的影响程度和系统地改变抑制性声刺激的强度 ,可在兴奋性频率调谐曲线或兴奋区的高频边或 /和低频边测出抑制性频率调谐曲线或抑制区 ;当这种抑制性输入被抑制性声刺激激活后 ,能降低阈上 10dB声强引起的兴奋反应的发放率 ,抑制效率随抑制声刺激强度的增强而加强 ;电泳GABAa受体拮抗剂荷包牡丹碱Bic后 ,可不同程度地去GABA能抑制 ,扩宽频率调谐曲线 ,使多峰调谐曲线变成单峰 ,封闭型变成开放型。表明GABA能抑制参与构成至AC神经元的抑制性输入 ,在正常情况下这种抑制有助于提高中枢听神经元的信号 /噪声比和频率分析能力 ,并锐化频率调谐。因此本结果提示 ,声音的各参量中所包含的信息从外周传入中枢后 。Nine adult big brown bats were used in this experiment.The GABAergic inhibition sharpening the frequency tuning of primary auditory cortical (AC) neurons was studied with the multi barrel electrode for iontophoresis and two tone stimulation method.We observed that excitatory frequency tuning curves appeared three types: the single peak opening, multi peak opening, and single peak closed.The inhibitory inputs to AC neurons could be activated by inhibitory tone and they had their best frequencies.The inhibitory frequency tuning curve or inhibitory frequency intensity response area at the low limb or/and high limb of an excitatory frequency tuning curve could be tested and obtained according to effective degree of GABAergic inhibition on the excitatory response induced by the tone of 10 dB above minimum threshold and by systematic change of inhibitory tone intensity.The result showed that GABAergic inhibition could decrease the firing rate of excitatory response to 10 dB stimulation above minimum threshold and increase the inhibitory effectiveness with the elevation of inhibitory tone intensity.GABAergic inhibition disinhibited during iontophoresis of bicuculline could make the excitatory frequency tuning curve to become the wider, the multi peak tuning curve to become the single peak, and single peak closed tuning curve to become the single peak opening tuning curve.Therefore, the results described above demonstrated that GABAergic inhibition participate in the formation of inhibitory input to AC neuron, it could help to sharpen the frequency tuning of the central auditory neurons, and this is the reason that frequency tuning curves become the “pencil shaped” and “spindle shaped”, and that central frequency tuning is more sensitive than peripheral.

关 键 词：γ-氨基丁酸 大棕蝠 听皮层 神经元 频率调谐 GABA能抑制 AC神经元 

分 类 号：Q62[生物学—生物物理学]