单耳堵塞对鼠耳蝠（Myotis chinensis）中脑下丘神经元听空间反应特性发育的影响及其机制研究
摘要
实验采用常规电生理学方法及免疫组织化学方法研究了单耳堵塞对鼠耳蝠(Myotis chinensis)中脑下丘听神经元空间反应特性发育的影响及其机制。主要内容包括：
一、鼠耳蝠中脑下丘神经元的听空间反应特性
实验在6只成年鼠耳蝠上进行。采用移动式声刺激装置，高频扬声器置于动物头部正前方34厘米处，并通过两只步进马达，可在动物头部正前方的半球面上移动。玻璃微电极细胞外记录下丘神经元对超声信号的反应。实验共观察了142个神经元的听空间反应特性。结果表明，这些神经元听反应中心的分布相当集中，多数(87.32％)位于听空间水平方向对侧10—40度，垂直方向下侧5—25度范围内；听反应中心的分布与神经元的最佳频率、记录深度之间的相关关系不明显；刺激声源位于听空间反应域的不同位置，神经元的反应水平不同，当刺激声源靠近听反应中心时，神经元听反应的放电脉冲数较多，随着声源远离反应中心，脉冲数逐渐减少；听空间反应域的大小与声刺激强度有关，随着声刺激强度的增加，听反应域逐渐增大；听空间反应域的大小还与神经元的最佳频率有关，最佳频率在该种蝙蝠的特征频率段(30.0—45.0 kHz)的神经元反应域明显比其它频段神经元小。
二、单耳堵塞对鼠耳蝠中脑下丘神经元听空间反应特性发育的影响
实验在移动式声刺激条件下，采用常规电生理学方法研究了单耳堵塞对鼠耳蝠中脑下丘神经元听空间反应特性发育的影响。实验在12只动物上进行，其中6只为对照组，实验前不久捕于皖南山区的岩洞中。6只为实验组，分别在动物出生后10天用泡沫塑料、牙科水泥及502胶水将其一侧外耳道堵塞，每天检查直到成年进行实验。实验分别记录了对照组动物及实验组动物在耳塞去除前后下丘
神经元的听空间反应特性，包括听反应中心的分布、听空间反应域的大小、水平
方位一阈值曲线及水平方位一放电脉冲数曲线等。对实验组动物，记录在堵塞耳
的对侧下丘进行。结果表明，单耳堵塞虽然不影响下丘神经元听反应最佳频率及
潜伏期的分布，但却提高了神经元听反应的最低阈值，同时改变了其听空间反应
特性，使得实验组动物堵塞耳对侧下丘神经元耳塞去除后与去除前及对照组动物
相比，听反应中心的分布较分散，听空间反应域较大，水平方位一阈值曲线较平
坦，水平方位一放电脉冲数曲线较宽。结果提示，单耳堵塞后中枢中与下丘神经
元听空间反应特性相关的神经环路经历了相应的变化，以补偿由于单耳堵塞造成
的不平衡的双耳偏差，这进一步证实了早期听觉经验对中枢听觉系统结构和功能
正常发育的重要性。
5、GABA及其受体抬抗剂bicuculline对幼年鼠耳蝇中脑下丘神经元听空间反
应特性的影响
实验采用微电泳技术考察了GABA及其A型受体抬抗剂荷包牡丹碱
（Bicuculline）对2周龄的幼年鼠耳幅中脑下丘神经元听空间反应特性的影响，
包括听空间反应域及方向敏感性等，并与成年动物进行了比较，为进一步了解下
丘中GABA能抑制在神经元听空间反应特性的形成和发育中的作用及单耳堵塞
对下丘神经元听空间反应特性产生影响的机制打下基础。实验在6只2周龄的幼
年动物和8只成年动物上进行。五管或三管玻璃微电极作细胞外记录及电泳。结
果表明，无论对幼年还是成年动物，微电泳GABA均可使下丘神经元的最低反
应阈值升高，听空间反应域的水平宽度减小，水平方位一阈值曲线的两臂变陡，
水平方位一放电脉冲数曲线变窄，说明神经元的方向敏感性提高。微电泳GABA＾
受体桔抗剂bicuculline可以使下丘神经元的最低反应阈值降低，听空间反应域的
水平宽度增大，水平方位一阈值曲线的两臂变平坦，水平方位一放电脉冲数曲线
变宽，说明神经元的方向敏感性降低。但是对不同年龄的动物，GABA及其
bicuculline的影响效应不同，对幼年动物的影响效应要明显低于成年动物。结果
提示，GABA能抑制在下丘神经元听空间反应特性的形成及发育过程中起了重
要作用，下丘中GABA能抑制性的改变可直接影响下丘神经元的听空间反应域
及方向敏感性。
四、单耳堵塞对鼠耳蝎中脑下丘GABA阳性反应神经元分布的影响
实验采用免疫组织化学技术考察了单耳堵塞对鼠耳幅中脑下丘中央核
GABA阳性反应神经元分布的影响，以期了解单耳堵塞对神经元听空间反应特性
2
产生影响的机制。实验在门只动物上进行，其中6只为对照组，出生后一直饲
养在正常环境中直到成年。5只为实验组，分别在动物出生后10天用泡沫塑料、
牙科水泥及502胶水将其一侧州耳道堵塞，每天检查直到成年进行实验。动物经
心脏灌流后取脑作冰冻切片
Using electrophysiological method and immunohistochemical technique, we studied the influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular neurons in bat, Myotis chinensis and the mechanism.The results were summarized as:
1.Auditor)' spatial response properties of inferior collicular neurons in bat, Myotis chinensis
Auditory spatial response properties of inferior collicular(IC) neurons of bat, Myotis chinensis, were studied using electrophysiological method under free-field conditions. The results showed that the distribution of response centers of 1C neurons was concentrated and most of them located within 10??40?contralateral in azimuth, 5??25?down in elevation of the frontal auditory space. The relationship between the locations of response centers of 1C neurons and their best frequencies(BFs) appeared to be less predicatable. The number of impulses of neuron varied when the acoustic stimulus was delivered from different positions within its auditory spatial response area. The auditory spatial response area expended asymmetrically with the stimulus intensity and there was relation between the size of auditory spatial response area and neuron's BF.
2.Influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular neurons in bat, Myotis chinensis
Under free-field conditions.we studied the influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular(IC) neurons in bat, Myotis chinensis using electrophysiological method. The results showed that monaural plugging did not alter the distribution of best frequency(BF) and latency of 1C neurons, but it raised the minimum threshold(MT) of 1C neurons. The monaural plugging also appeared to modify the auditory spatial response
properties of 1C neurons. Thus, when the earplug was removed, the response centers of 1C neurons contralateral to plugged ear were scattered over a wider area of auditor}' space than when the earplug was intact and the control bats. Furthermore, the sizes of auditory spatial response areas were bigger and the variations in MT and number of impulses to a BF sound delivered from different azimuthal angles within the response area were flatter. These results suggest that the neural circuits underlying auditory spatial response properties of 1C neurons of monaural plugged bats undergone modifications to compensate for the unatural binaural disparity during postnatal development and the}' also suggest the importance of early auditory experence to postnatal development of central auditor}' system.
3.Effects of GABA and bicuculline on auditor}' spatial response properties of inferior collicular neurons in juvenile and adult bats, Myotis chinensis
Using iontophoretic technique, we studied the effects of GABA and GABAA antagonist, bicuculline, on auditory spatial response properties of inferior collicular(IC) neurons in juvenile and adult bats, Myotis chinensis. The results showed that application of GABA increased the lowest minimum threshold(the lowest MT) of 1C neurons, broadened the auditory spatial response areas,sharpened the auditory spatial sensitivity curves as determined by variation of MT as a function of azimuthal angle and narrowed auditor}' spatial sensitivity curves as determined by variation of number of impulses as a function of azimuthal angle, while application of GABAA antagonist, bicuculline,reversed the above effecets.Furthermore,there was difference between the effects of GABA and bicuculline on the juvenile and adult bats. These data suggest that GABAergic inhibition play an important role on the form of auditory spatial response properties of 1C neurons and the changes of the GABAergic inhibition can modify the auditory spatial response areas and spatial sensitivities of 1C neurons.
4.Effects of monaural plugging on the distribution of GABA-immunopositive neurons in the inferior colliculus of bat, Myotis chinensis
In order to explore the
一、鼠耳蝠中脑下丘神经元的听空间反应特性
实验在6只成年鼠耳蝠上进行。采用移动式声刺激装置，高频扬声器置于动物头部正前方34厘米处，并通过两只步进马达，可在动物头部正前方的半球面上移动。玻璃微电极细胞外记录下丘神经元对超声信号的反应。实验共观察了142个神经元的听空间反应特性。结果表明，这些神经元听反应中心的分布相当集中，多数(87.32％)位于听空间水平方向对侧10—40度，垂直方向下侧5—25度范围内；听反应中心的分布与神经元的最佳频率、记录深度之间的相关关系不明显；刺激声源位于听空间反应域的不同位置，神经元的反应水平不同，当刺激声源靠近听反应中心时，神经元听反应的放电脉冲数较多，随着声源远离反应中心，脉冲数逐渐减少；听空间反应域的大小与声刺激强度有关，随着声刺激强度的增加，听反应域逐渐增大；听空间反应域的大小还与神经元的最佳频率有关，最佳频率在该种蝙蝠的特征频率段(30.0—45.0 kHz)的神经元反应域明显比其它频段神经元小。
二、单耳堵塞对鼠耳蝠中脑下丘神经元听空间反应特性发育的影响
实验在移动式声刺激条件下，采用常规电生理学方法研究了单耳堵塞对鼠耳蝠中脑下丘神经元听空间反应特性发育的影响。实验在12只动物上进行，其中6只为对照组，实验前不久捕于皖南山区的岩洞中。6只为实验组，分别在动物出生后10天用泡沫塑料、牙科水泥及502胶水将其一侧外耳道堵塞，每天检查直到成年进行实验。实验分别记录了对照组动物及实验组动物在耳塞去除前后下丘
神经元的听空间反应特性，包括听反应中心的分布、听空间反应域的大小、水平
方位一阈值曲线及水平方位一放电脉冲数曲线等。对实验组动物，记录在堵塞耳
的对侧下丘进行。结果表明，单耳堵塞虽然不影响下丘神经元听反应最佳频率及
潜伏期的分布，但却提高了神经元听反应的最低阈值，同时改变了其听空间反应
特性，使得实验组动物堵塞耳对侧下丘神经元耳塞去除后与去除前及对照组动物
相比，听反应中心的分布较分散，听空间反应域较大，水平方位一阈值曲线较平
坦，水平方位一放电脉冲数曲线较宽。结果提示，单耳堵塞后中枢中与下丘神经
元听空间反应特性相关的神经环路经历了相应的变化，以补偿由于单耳堵塞造成
的不平衡的双耳偏差，这进一步证实了早期听觉经验对中枢听觉系统结构和功能
正常发育的重要性。
5、GABA及其受体抬抗剂bicuculline对幼年鼠耳蝇中脑下丘神经元听空间反
应特性的影响
实验采用微电泳技术考察了GABA及其A型受体抬抗剂荷包牡丹碱
（Bicuculline）对2周龄的幼年鼠耳幅中脑下丘神经元听空间反应特性的影响，
包括听空间反应域及方向敏感性等，并与成年动物进行了比较，为进一步了解下
丘中GABA能抑制在神经元听空间反应特性的形成和发育中的作用及单耳堵塞
对下丘神经元听空间反应特性产生影响的机制打下基础。实验在6只2周龄的幼
年动物和8只成年动物上进行。五管或三管玻璃微电极作细胞外记录及电泳。结
果表明，无论对幼年还是成年动物，微电泳GABA均可使下丘神经元的最低反
应阈值升高，听空间反应域的水平宽度减小，水平方位一阈值曲线的两臂变陡，
水平方位一放电脉冲数曲线变窄，说明神经元的方向敏感性提高。微电泳GABA＾
受体桔抗剂bicuculline可以使下丘神经元的最低反应阈值降低，听空间反应域的
水平宽度增大，水平方位一阈值曲线的两臂变平坦，水平方位一放电脉冲数曲线
变宽，说明神经元的方向敏感性降低。但是对不同年龄的动物，GABA及其
bicuculline的影响效应不同，对幼年动物的影响效应要明显低于成年动物。结果
提示，GABA能抑制在下丘神经元听空间反应特性的形成及发育过程中起了重
要作用，下丘中GABA能抑制性的改变可直接影响下丘神经元的听空间反应域
及方向敏感性。
四、单耳堵塞对鼠耳蝎中脑下丘GABA阳性反应神经元分布的影响
实验采用免疫组织化学技术考察了单耳堵塞对鼠耳幅中脑下丘中央核
GABA阳性反应神经元分布的影响，以期了解单耳堵塞对神经元听空间反应特性
2
产生影响的机制。实验在门只动物上进行，其中6只为对照组，出生后一直饲
养在正常环境中直到成年。5只为实验组，分别在动物出生后10天用泡沫塑料、
牙科水泥及502胶水将其一侧州耳道堵塞，每天检查直到成年进行实验。动物经
心脏灌流后取脑作冰冻切片
Using electrophysiological method and immunohistochemical technique, we studied the influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular neurons in bat, Myotis chinensis and the mechanism.The results were summarized as:
1.Auditor)' spatial response properties of inferior collicular neurons in bat, Myotis chinensis
Auditory spatial response properties of inferior collicular(IC) neurons of bat, Myotis chinensis, were studied using electrophysiological method under free-field conditions. The results showed that the distribution of response centers of 1C neurons was concentrated and most of them located within 10??40?contralateral in azimuth, 5??25?down in elevation of the frontal auditory space. The relationship between the locations of response centers of 1C neurons and their best frequencies(BFs) appeared to be less predicatable. The number of impulses of neuron varied when the acoustic stimulus was delivered from different positions within its auditory spatial response area. The auditory spatial response area expended asymmetrically with the stimulus intensity and there was relation between the size of auditory spatial response area and neuron's BF.
2.Influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular neurons in bat, Myotis chinensis
Under free-field conditions.we studied the influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular(IC) neurons in bat, Myotis chinensis using electrophysiological method. The results showed that monaural plugging did not alter the distribution of best frequency(BF) and latency of 1C neurons, but it raised the minimum threshold(MT) of 1C neurons. The monaural plugging also appeared to modify the auditory spatial response
properties of 1C neurons. Thus, when the earplug was removed, the response centers of 1C neurons contralateral to plugged ear were scattered over a wider area of auditor}' space than when the earplug was intact and the control bats. Furthermore, the sizes of auditory spatial response areas were bigger and the variations in MT and number of impulses to a BF sound delivered from different azimuthal angles within the response area were flatter. These results suggest that the neural circuits underlying auditory spatial response properties of 1C neurons of monaural plugged bats undergone modifications to compensate for the unatural binaural disparity during postnatal development and the}' also suggest the importance of early auditory experence to postnatal development of central auditor}' system.
3.Effects of GABA and bicuculline on auditor}' spatial response properties of inferior collicular neurons in juvenile and adult bats, Myotis chinensis
Using iontophoretic technique, we studied the effects of GABA and GABAA antagonist, bicuculline, on auditory spatial response properties of inferior collicular(IC) neurons in juvenile and adult bats, Myotis chinensis. The results showed that application of GABA increased the lowest minimum threshold(the lowest MT) of 1C neurons, broadened the auditory spatial response areas,sharpened the auditory spatial sensitivity curves as determined by variation of MT as a function of azimuthal angle and narrowed auditor}' spatial sensitivity curves as determined by variation of number of impulses as a function of azimuthal angle, while application of GABAA antagonist, bicuculline,reversed the above effecets.Furthermore,there was difference between the effects of GABA and bicuculline on the juvenile and adult bats. These data suggest that GABAergic inhibition play an important role on the form of auditory spatial response properties of 1C neurons and the changes of the GABAergic inhibition can modify the auditory spatial response areas and spatial sensitivities of 1C neurons.
4.Effects of monaural plugging on the distribution of GABA-immunopositive neurons in the inferior colliculus of bat, Myotis chinensis
In order to explore the
引文
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2. Fuzessery,Z.M. and Pollak,G.D.(1985)Determinants of sound location selectivity in bat inferior colliculus: a combined dichotic and free-field stimulation study, J. Neurophysiol. 54:757-781.
3. Fuzessery,Z.M., Wenstrup,J.J., and Pollak,G.D.(1985)A representation of horizontal sound location in the inferior colliculus of mustache bat(Pteronotus p.parnellii),Hearing Res.20:85-89.
4. Jen,P.H.-S.(1980)Coding of directional information by single neurons of the Ssegment of the FM bat,Myotis lucifugus,J.Exp. Biol.34:1O1-118.
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13. Moore,D.R., Hutchings,M.E.,Addison,P.D.,Semple,N.M. and Aitkin,L.M.(1984) Properties of spatial receptive fields in the cat inferior colliculus. Ⅱ.Stimulus intensity effects,Hearing Res. 13:175-188.
14. Poon,P.W.F.,Sun,X.D.,Kamada, T. and Jen,P.H.-S.(1990)Frequency and space representation in the inferior colliculus of the FM bat,Eptesicus fuscus, Exp. Brain Res. 79:83-91.
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16. Schuller,G. and Pollak,G.(1979)Disproportionate frequency representation in the inferior colliculus of doppler-compensating greater horseshoe bats:evidence of an acoustic fovea, J.Comp. Physiol. 132:47-54.
17. Shimozawa,T.,Sun,X.D. and Jen,P.H.-S.(1984)Auditory space representation in the superior colliculus of the big brown bat,Eptesicusfuscus,Brain Res.311:289-296.
18. Suga,N.(1964)Single unit activity in cochlear nucleus and inferior colliculus of echolocating bats, J. Physiol. 172:449-474.
19. Sun,X.D.and Jen,P.H.-S.(1987)Pinna position affects the auditory space representation in the inferior colliculus of the FM bat,Eptesicus fuscus,Hearing Res.27:207-219.
20. Sun,X.D.,Jen,P.H.-S. and Zhang,W.P.(1987)Auditory spatial response areas of single neurons and representation in the cerebellum of echolocating bats,Brain Res. 414: 314-322.
21．孙心德，章森福(1982)菊头蝠捕食时对障碍物的回避能力，兽类学报，2(2)：139-142．
22．孙心德，李华，黄宏(1987)菊头蝠耳廓方位对障碍回避能力的影响，兽类学报，7(1)：8-12．
23．孙心德，章森福，周华，姜勤，顾龙(1988)鲁氏菊头蝠回避障碍时抗干扰能力的研究，兽类学报，8(1)：21-24．
24．林龙年，孙心德(1996)幼年蝙蝠下丘神经元的听空间特性，生物物理学报，12(2)：258-262．
2. Fuzessery,Z.M. and Pollak,G.D.(1985)Determinants of sound location selectivity in bat inferior colliculus: a combined dichotic and free-field stimulation study, J. Neurophysiol. 54:757-781.
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21．孙心德，章森福(1982)菊头蝠捕食时对障碍物的回避能力，兽类学报，2(2)：139-142．
22．孙心德，李华，黄宏(1987)菊头蝠耳廓方位对障碍回避能力的影响，兽类学报，7(1)：8-12．
23．孙心德，章森福，周华，姜勤，顾龙(1988)鲁氏菊头蝠回避障碍时抗干扰能力的研究，兽类学报，8(1)：21-24．
24．林龙年，孙心德(1996)幼年蝙蝠下丘神经元的听空间特性，生物物理学报，12(2)：258-262．