Li L, Korngut L M, Frost B J, Beninger R J
Department of Psychology, Queen's University, Kingston, Ontario, Canada.
Physiol Behav. 1998 Aug;65(1):133-9. doi: 10.1016/s0031-9384(98)00143-7.
The magnitude of the acoustic startle response can be reduced by a relatively weak sound presented immediately before the startle-eliciting sound; this phenomenon has been termed prepulse inhibition (PPI). Previous studies reported that PPI was present in the decerebrate rat, indicating that the primary neural pathways mediating PPI are located in the brainstem. The present study investigated the effects of focal excitotoxic lesions of the inferior colliculus (IC) on acoustic PPI in rats. In the first part, startle magnitudes were measured in six normal rats as the interstimulus interval (ISI) between the prepulse and startle-eliciting sounds varied between 10 and 100 ms. Prepulse-inhibited startle changed in an ISI-dependent manner with the most effective ISI at 50 ms. In the second part, 21 rats were assigned to three groups: normal unoperated, cortical lesion, and IC lesion. With the ISI fixed at 50 ms, as the prepulse sound level increased from 29 to 49 dB SPL, startle responses decreased quickly in both normal and cortical lesion rats. However, rats with unilateral IC lesions made with ibotenic acid had significantly lower PPI but did not display any increase in startle magnitude. These data suggest that the IC is an important structure in the neural circuit mediating acoustic PPI.
在惊吓诱发声音之前立即呈现相对较弱的声音，可以降低听觉惊吓反应的幅度；这种现象被称为前脉冲抑制（PPI）。先前的研究报道，去大脑大鼠存在PPI，这表明介导PPI的主要神经通路位于脑干。本研究调查了下丘（IC）局灶性兴奋性毒性损伤对大鼠听觉PPI的影响。在第一部分中，测量了六只正常大鼠在预脉冲和惊吓诱发声音之间的刺激间隔（ISI）在10至100毫秒之间变化时的惊吓幅度。预脉冲抑制的惊吓以ISI依赖的方式变化，最有效的ISI为50毫秒。在第二部分中，将21只大鼠分为三组：正常未手术组、皮质损伤组和IC损伤组。将ISI固定在50毫秒，随着预脉冲声级从29分贝声压级增加到49分贝声压级，正常大鼠和皮质损伤大鼠的惊吓反应均迅速降低。然而，用鹅膏蕈氨酸造成单侧IC损伤的大鼠的PPI显著降低，但惊吓幅度没有任何增加。这些数据表明，IC是介导听觉PPI的神经回路中的一个重要结构。
