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GABA能抑制调制大棕蝠下丘神经元对串声刺激的强度敏感性

栾瑞红, 吴飞健, Philip H.-S.Jen, 孙心德

华东师范大学生命科学学院.上海 200062；华中师范大学生命科学学院.湖北,武汉 430079；密苏里大学哥伦比亚分校生物学系.密苏里州 65211

摘要

该文采用不同重复率的串声刺激,模拟大棕蝠回声定位不同阶段听到的调频声纳信号,利用电生理方法和微电泳技术研究不同重复率串刺激条件下GABA能抑制对下丘神经元强度敏感性的影响。结果发现,随串刺激重复率的增加,有的神经元强度敏感性增强,有的神经元强度敏感性则降低。在不同串刺激条件下,微电泳荷包牡丹碱,神经元放电率均增加,随重复率增加强度敏感性增强或减弱的趋势消失,提示GABA能抑制调制下丘神经元对不同重复率串刺激反应的强度敏感性。串刺激强度在最低阈值附近时,微电泳荷包牡丹碱导致放电率增加的百分率最大,随串刺激强度增加,放电率增加的百分率逐渐减小。提示刺激强度较低时,GABA能抑制对下丘神经元强度敏感性的影响更有效。

关键词： 蝙蝠; 强度敏感性; 下丘; 重复率; 回声定位

GABAergic inhibition modulates intensity sensitivity of temporally patterned pulse trains in the inferior collicular neurons in big brown bats

Luan Ruihong, Wu Feijian, Philip H.-S.Jen, Sun Xinde

School of Life Sciences, East China Normal University.Shanghai 200062；China；Division of Biological Sciences, University of Missouri-Columbia, MO 65211

Abstract

The echolocating big brown bats （Eptesicusfuscus） emit trains of frequency-modulated （FM） biosonar signals with duration, amplitude, repetition rate, and sweep structure changing systematically during interception of their prey. In the present study, the sound stimuli of temporally patterned pulse trains at three different pulse repetition rates （PRRs） were used to mimic the sounds received during search, approach, and terminal stages of echolocation. Electrophysiological method was adopted in recordings from the inferior colliculus （IC） of midbrain. By means of iontophoretic application of bicuculline, the effect of GABAergic inhibition on the intensity sensitivity of IC neurons responding to three different PRRs of 10, 30 and 90 pulses per second （pps） was examined. The rate-intensity functions （RIFs） were acquired. The dynamic range （DR） of RIFs was considered as a criterion of intensity sensitivity. Comparing the average DR of RIFs at different PRRs, we found that the intensity sensitivity of some neurons improved, but that of other neurons decayed when repetition rate of stimulus trains increased from 10 to 30 and 90 pps. During application of bicuculline, the number of impulses responding to the different pulse trains increased under all stimulating conditions, while the DR differences of RIFs at different PRRs were abolished. The results indicate that GABAergic inhibition was involved in modulating the intensity sensitivity of IC neurons responding to pulse trains at different PRRs. Before and during bicuculline application, the percentage of changes in responses was maximal in lower stimulus intensity near to the minimum threshold （MT）, and decreased gradually with the increment of stimulus intensity. This observation suggests that GABAergic inhibition contributes more effectively to the intensity sensitivity of the IC neurons responding to pulse trains at lower sound level.

Key words: bat;intensity sensitivity;inferior colliculus;pulse repetition rate;echolocation

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引用本文：

栾瑞红, 吴飞健, Philip H.-S.Jen, 孙心德. GABA能抑制调制大棕蝠下丘神经元对串声刺激的强度敏感性[J]. 生理学报 2007; 59 (6): 805-813.

Luan Ruihong, Wu Feijian, Philip H.-S.Jen, Sun Xinde. GABAergic inhibition modulates intensity sensitivity of temporally patterned pulse trains in the inferior collicular neurons in big brown bats. Acta Physiol Sin 2007; 59 (6): 805-813 (in Chinese with English abstract).