Szczepaniak W S, Møller A R
Department of Neurological Surgery, University of Pittsburgh School of Medicine, PA 15213, USA.
Neurosci Lett. 1995 Aug 18;196(1-2):77-80. doi: 10.1016/0304-3940(95)11851-m.
Many investigations have shown that modulation of sensory input, either by over stimulation or sensory deprivation, can cause a reorganization of structures located high in the central nervous system (CNS). Although most of these studies had focused on studying changes in the function and tonotopic organization of the sensory cortex, recent evidence has suggested that plastic changes in specific subcortical nuclei of sensory systems may also occur in response to modulation of sensory input, and may be partially responsible for changes reflected at the level of the cortex. In the present study we investigated the effects of noise exposure (4-kHz continuous tone at 104 dB sound pressure level (SPL) for 30 min duration) on the processing of auditory information at the level of the inferior colliculus (IC). We studied how evoked potentials recorded from the surface of the IC changed as a function of the duration of the tone bursts used as stimuli. We measured the amplitude of a peak that is generated postsynaptically in the IC in response to tone bursts between 1 and 6 ms duration. In animals that were not exposed to the tone, the amplitude of this peak decreased with increasing stimulus duration, but after tone exposure, the decrease in the amplitude of this peak was significantly less than in the animals not exposed to the tone. A microinjection of the GABAA antagonist, bicucullene, into the IC in the animals not exposed to the tone caused the amplitude of the peak to be less dependent on tone burst duration, which indicates that the decrease in the amplitude of this component of the response from the IC with increasing stimulus duration is a result of GABAA mediated inhibition on IC neurons. The tone exposure caused a similar decrease in amplitude of this component of the response from the IC, thus indicating that noise exposure reduced the GABAA mediated component of this function. This is supported by the finding that microinjections of bicucullene into the IC of noise-exposed animals did not significantly change the relationship between the amplitude of this peak and the stimulus duration.
许多研究表明，通过过度刺激或感觉剥夺对感觉输入进行调制，可导致位于中枢神经系统（CNS）高位的结构发生重组。尽管这些研究大多集中在研究感觉皮层功能和音调组织的变化，但最近的证据表明，感觉系统特定皮层下核团的可塑性变化也可能因感觉输入的调制而发生，并且可能部分地导致皮层水平所反映的变化。在本研究中，我们调查了噪声暴露（104分贝声压级（SPL）的4千赫连续音调，持续30分钟）对下丘（IC）水平听觉信息处理的影响。我们研究了从IC表面记录的诱发电位如何随用作刺激的音爆持续时间而变化。我们测量了IC中突触后产生的一个峰值的幅度，该峰值响应持续时间在1至6毫秒之间的音爆。在未暴露于该音调的动物中，该峰值的幅度随刺激持续时间的增加而降低，但在音调暴露后，该峰值幅度的降低明显小于未暴露于该音调的动物。向未暴露于该音调的动物的IC中微量注射GABAA拮抗剂荷包牡丹碱，导致该峰值的幅度对音爆持续时间的依赖性降低，这表明随着刺激持续时间的增加，IC响应的该成分幅度的降低是GABAA介导的对IC神经元抑制的结果。音调暴露导致IC响应的该成分幅度出现类似的降低，从而表明噪声暴露降低了该功能的GABAA介导成分。这一发现得到了支持，即向噪声暴露动物的IC中微量注射荷包牡丹碱并没有显著改变该峰值幅度与刺激持续时间之间的关系。
