Reduced tolerance to sound stimuli (hyperacusis) is commonly seen in tinnitus patients. Dysfunction of limbic systems, such as the nucleus accumbens (NAc), may be involved in emotional reactions to the sound stimuli in tinnitus patients. To study the functional changes in the NAc in hyperacusis, we have examined the neural activity changes of the NAc using c-Fos staining in an animal model of hyperacusis. The c-Fos staining was also examined in the medial geniculate nucleus (MGN), a central auditory pathway which has neural projections to the NAc. Postnatal rats (14 days) were exposed to loud noise (115 dB SPL, 4 hours for two consecutive days) to induce hyperacusis (). Rats without noise exposure were used as the controls (). After P35, rats in both groups were put in a behavioral training for sound detection. After they were trained to detect sound stimuli, their reaction time to noise bursts centered at 2 kHz (40-110 dB SPL) was measured. Rats in the noise group showed a significantly shorter reaction time than those in the control group to the noise bursts at high intensities, suggesting the noise exposure induced hyperacusis behavior. The c-Fos expressions in the NAc and the MGNs of the noise group were significantly higher than those of the control group. Our results suggested that early-age noise exposure caused hyperactivity in the NAc and the MGNs which may induce the loudness increase in these rats.

中文翻译：

---

伏隔核的过度兴奋与噪声引起的听觉过敏有关


对声音刺激的耐受性降低（听觉过敏）常见于耳鸣患者。边缘系统的功能障碍，例如伏隔核（NAc），可能与耳鸣患者对声音刺激的情绪反应有关。为了研究听觉过敏中 NAc 的功能变化，我们使用 c-Fos 染色在听觉过敏动物模型中检查了 NAc 的神经活动变化。还在内侧膝状核 (MGN) 中检查了 c-Fos 染色，MGN 是一种中枢听觉通路，具有到 NAc 的神经投射。出生后（14天）的大鼠暴露于大声噪音（115 dB SPL，连续两天4小时）以诱发听觉过敏（ ）。没有暴露于噪音的大鼠被用作对照（ ）。 P35后，两组大鼠均接受声音检测行为训练。在训练它们检测声音刺激后，测量了它们对以 2 kHz (40-110 dB SPL) 为中心的噪声突发的反应时间。噪声组的大鼠对高强度噪声爆发的反应时间明显短于对照组，这表明噪声暴露诱发了听觉过敏行为。噪声组NAc和MGNs中c-Fos的表达显着高于对照组。我们的结果表明，早期的噪音暴露会导致 NAc 和 MGN 过度活跃，这可能会导致这些大鼠的响度增加。