Gómez-Nieto Ricardo, Sinex Donal G, Horta-Júnior José de Anchieta C, Castellano Orlando, Herrero-Turrión Javier M, López Dolores E
Neuroscience Institute of Castilla y León (INCyL), University of Salamanca, 37007, Salamanca, Spain.
Brain Struct Funct. 2014 Sep;219(5):1555-73. doi: 10.1007/s00429-013-0585-8. Epub 2013 Jun 4.
Cochlear root neurons (CRNs) are the first brainstem neurons which initiate and participate in the full expression of the acoustic startle reflex. Although it has been suggested that a cholinergic pathway from the ventral nucleus of the trapezoid body (VNTB) conveys auditory prepulses to the CRNs, the neuronal origin of the VNTB-CRNs projection and the role it may play in the cochlear root nucleus remain uncertain. To determine the VNTB neuronal type which projects to CRNs, we performed tract-tracing experiments combined with mechanical lesions, and morphometric analyses. Our results indicate that a subpopulation of non-olivocochlear neurons projects directly and bilaterally to CRNs via the trapezoid body. We also performed a gene expression analysis of muscarinic and nicotinic receptors which indicates that CRNs contain a cholinergic receptor profile sufficient to mediate the modulation of CRN responses. Consequently, we investigated the effects of auditory prepulses on the neuronal activity of CRNs using extracellular recordings in vivo. Our results show that CRN responses are strongly inhibited by auditory prepulses. Unlike other neurons of the cochlear nucleus, the CRNs exhibited inhibition that depended on parameters of the auditory prepulse such as intensity and interstimulus interval, showing their strongest inhibition at short interstimulus intervals. In sum, our study supports the idea that CRNs are involved in the auditory prepulse inhibition of the acoustic startle reflex, and confirms the existence of multiple cholinergic pathways that modulate the primary acoustic startle circuit.
耳蜗根神经元（CRNs）是启动并参与听觉惊吓反射完全表达的首批脑干神经元。尽管有人提出，来自斜方体腹侧核（VNTB）的胆碱能通路将听觉预脉冲传递至CRNs，但VNTB-CRNs投射的神经元起源及其在耳蜗根核中可能发挥的作用仍不明确。为了确定投射至CRNs的VNTB神经元类型，我们进行了结合机械损伤的示踪实验和形态计量分析。我们的结果表明，非橄榄耳蜗神经元的一个亚群通过斜方体直接双侧投射至CRNs。我们还对毒蕈碱和烟碱受体进行了基因表达分析，结果表明CRNs含有足以介导CRN反应调节的胆碱能受体谱。因此，我们在体内使用细胞外记录方法研究了听觉预脉冲对CRNs神经元活动的影响。我们的结果表明，CRN反应受到听觉预脉冲的强烈抑制。与耳蜗核的其他神经元不同，CRNs表现出的抑制作用取决于听觉预脉冲的参数，如强度和刺激间隔，在短刺激间隔时抑制作用最强。总之，我们的研究支持CRNs参与听觉惊吓反射的听觉预脉冲抑制这一观点，并证实了存在多条调节初级听觉惊吓回路的胆碱能通路。
