Brandão M L, Coimbra N C, Osaki M Y
Laboratório de Psicobiologia, FFCLRP, Campus University of São Paulo, Avenida Bandeirantes 3900, 14049-901 Ribeirão Prêto, São Paulo, Brazil.
Physiol Behav. 2001 Feb;72(3):365-72. doi: 10.1016/s0031-9384(00)00418-2.
It is long established that the inferior colliculus is involved in conveying all kinds of auditory information to higher cortical structures. Moreover, gradual increases in the electrical stimulation of this structure produces progressive aversive responses from vigilance, through freezing, until escape. Recently, we have shown that microinjections of the excitatory amino acids, N-methyl-D-aspartate (NMDA) and glutamate, into the inferior colliculus mimic these aversive effects. In the present study, we extend these observations showing that unilateral microinjections of 5 nmol of glutamate into the inferior colliculus--a dose that causes freezing behavior--in rats with bilateral recording electrodes into this structure produce an increase in the magnitude of the collicular-evoked potential in the ipsilateral side of the injection in relation to saline-injected animals. Besides, the application of two kinds of fear-evoking stimulations--light as a conditioned stimuli (CS) and ultrasound signals at the frequency of 22 kHz--also produced an increase in the amplitude of the evoked potentials recorded from the inferior colliculus in comparison to control situations without aversive stimuli presentations. These data support previous reports showing that fast-acting excitatory amino acid receptors in this midbrain region are involved in the processing of auditory information. Moreover, fear-eliciting stimulations, such as light-CS and ultrasound signals, increase acoustically evoked firing of neurons in the central nucleus of the inferior colliculus of rats.
长期以来人们已确定，下丘参与将各种听觉信息传递至更高的皮质结构。此外，对该结构进行电刺激时，刺激强度逐渐增加会引发渐进性的厌恶反应，从警觉开始，经僵立反应，直至逃跑。最近，我们发现向下丘微量注射兴奋性氨基酸N-甲基-D-天冬氨酸（NMDA）和谷氨酸，会模拟出这些厌恶效应。在本研究中，我们进一步拓展了这些观察结果，表明在双侧记录电极植入下丘的大鼠中，向下丘单侧微量注射5 nmol谷氨酸（此剂量会引发僵立行为），相较于注射生理盐水的动物，会使注射侧同侧下丘诱发电位的幅度增加。此外，与未呈现厌恶刺激的对照情况相比，施加两种引发恐惧的刺激——作为条件刺激（CS）的光和频率为22 kHz的超声信号，也会使下丘记录到的诱发电位幅度增加。这些数据支持了先前的报告，即该中脑区域中快速起效的兴奋性氨基酸受体参与了听觉信息的处理。此外，引发恐惧的刺激，如光-CS和超声信号，会增加大鼠下丘中央核中神经元的听觉诱发放电。
