Luo Hao, Pace Edward, Zhang Xueguo, Zhang Jinsheng
Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine, Detroit, Michigan.
J Neurosci Res. 2014 Nov;92(11):1466-77. doi: 10.1002/jnr.23424. Epub 2014 Jun 17.
Exposure to high-pressure blast shock waves is known to cause tinnitus. Although the underlying mechanisms may involve damage to structures in the ear and/or direct brain impact, which triggers a cascade of neuroplastic changes in both auditory and nonauditory centers, it remains unclear how the induced neuroplasticity manifests neurophysiologically. This study investigates the influence of blast exposure on spontaneous firing rates (SFRs) in the dorsal cochlear nucleus (DCN) and its time course in rats with blast-induced tinnitus. Each rat was exposed to a single blast at 22 psi. Behavioral evidence of tinnitus was measured by using a gap-detection acoustic startle-reflex paradigm. SFRs were measured 1 day, 1 month, and 3 months after blast exposure. The results showed that nine rats with blast-induced tinnitus and hearing loss developed hyperactivity immediately and that the induced hyperactivity persisted in six rats with tinnitus at 1 month after blast exposure. At 3 months after blast exposure, however, the induced hyperactivity of four rats with tinnitus transitioned to hypoactivity. In addition, the 20-30-kHz, and >30-kHz regions in the DCN of rats with and without blast-induced tinnitus were more affected than other frequency regions at different recovery time points after blast exposure. These results demonstrate that the neural mechanisms underlying blast-induced tinnitus are substantially different from those underlying noise-induced tinnitus.
已知暴露于高压冲击波会导致耳鸣。尽管其潜在机制可能涉及耳部结构损伤和/或直接的脑部冲击，进而引发听觉和非听觉中枢的一系列神经可塑性变化，但目前尚不清楚所诱导的神经可塑性在神经生理学上是如何表现的。本研究调查了爆炸暴露对爆震性耳鸣大鼠背侧耳蜗核（DCN）自发放电率（SFRs）的影响及其时间进程。每只大鼠暴露于22磅力/平方英寸的单次爆炸中。通过使用间隙检测听觉惊吓反射范式来测量耳鸣的行为证据。在爆炸暴露后1天、1个月和3个月测量SFRs。结果显示，9只患有爆震性耳鸣和听力损失的大鼠立即出现活动亢进，并且在爆炸暴露后1个月，6只耳鸣大鼠中所诱导的活动亢进持续存在。然而，在爆炸暴露后3个月，4只耳鸣大鼠所诱导的活动亢进转变为活动减退。此外，在爆炸暴露后的不同恢复时间点，有爆震性耳鸣和无爆震性耳鸣大鼠的DCN中20 - 30千赫兹和>30千赫兹区域比其他频率区域受影响更大。这些结果表明，爆震性耳鸣的神经机制与噪声性耳鸣的神经机制有很大不同。
