The commissure of the inferior colliculus shapes frequency response areas in rat:: an in vivo study using reversible blockade with microinjection of kynurenic acid
The commissure of the inferior colliculus shapes frequency response areas in rat:: an in vivo study using reversible blockade with microinjection of kynurenic acid
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DOI：
10.1007/s00221-003-1615-1
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发表时间：
2003-12-01
影响因子：
2
通讯作者：
Rees, A
中科院分区：
文献类型：
--
作者：
Malmierca, MS;Hernández, O;Rees, A
下丘连合（CoIC）连接两个下丘（IC）中相应的频带层。虽然已经在体外对CoIC进行了神经生理学研究，但CoIC对IC神经元对生理刺激的反应的影响尚未得到解决。在这项研究中，我们将谷氨酸受体阻断剂犬尿烯酸注入一个IC，同时记录另一个IC神经元的频率响应面积（FRA），以验证IC神经元的频率响应特性受对侧IC连合输入影响的假设。在连合被阻断后，12个神经元中有10个表现出FRA的增加或减少。在大多数神经元（9/12）的反应面积变化在同一方向，无论是单耳刺激（在耳对侧记录IC）或双耳刺激的神经元。在一个神经元中，CoIC的阻断导致双耳刺激下反应区域的扩大和单耳刺激下的收缩。在其余两个单位中，未观察到影响。超过标准的反应区域的变化范围在单耳刺激的对照值的17%和80%之间，双耳刺激的对照值的35%和77%之间。面积的变化也可能伴随着穗率和单调性的变化。从我们的观察，FRA合同后连合块，我们推断，连合含有兴奋性纤维。然而，在其他情况下，反应区域的扩大表明连合也含有抑制纤维，或者其作用是由双突触和单突触回路介导的。由于样本量较小，无法得出哪种效应占主导地位的明确结论。我们的结论是，从对侧IC通过CoIC投射的输入影响IC中神经元的光谱选择性和响应增益。
The commissure of the inferior colliculus (CoIC) interconnects corresponding frequency-band laminae in the two inferior colliculi (ICs). Although the CoIC has been studied neurophysiologically in vitro, the effect of the CoIC on the responses of IC neurons to physiological stimuli has not been addressed. In this study, we injected the glutamate receptor blocker kynurenic acid into one IC while recording the frequency response areas (FRAs) of neurons in the other, to test the hypothesis that frequency response properties of IC neurons are influenced by commissural inputs from the contralateral IC. Following blockade of the commissure, 10 of 12 neurons tested exhibited an increase or a decrease in their FRAs. In most neurons (9/12) the response area changed in the same direction, irrespective of whether the neuron was stimulated monaurally (at the ear contralateral to the recorded IC) or binaurally. In one neuron, blockade of the CoIC resulted in an expansion of the response area under binaural stimulation and a contraction under monaural stimulation. In the remaining two units, no effect was observed. Changes in response areas that exceeded the criterion ranged between 17 and 80% of control values with monaural stimulation, and 35 and 77% with binaural stimulation. Area changes could also be accompanied by changes in spike rate and monotonicity. From our observation that FRAs contract following commissure block, we infer that the commissure contains excitatory fibres. The expansion of response areas in other cases, however, suggests that the commissure also contains inhibitory fibres, or that its effects are mediated by disynaptic as well as monosynaptic circuits. The small sample size precludes a definitive conclusion as to which effect predominates. We conclude that inputs from the contralateral IC projecting via the CoIC influence the spectral selectivity and response gain of neurons in the IC.