AUTHOR=Kou Zhen-Zhen , Qu Juan , Li Hui , Zhang Dong-Liang , Li Yun-Qing 

TITLE=Noise-induced hearing loss is correlated with alterations in the expression of GABAB receptors and PKC gamma in the murine cochlear nucleus complex

JOURNAL=Frontiers in Neuroanatomy

VOLUME=7

YEAR=2013

URL=https://www.frontiersin.org/journals/neuroanatomy/articles/10.3389/fnana.2013.00025

DOI=10.3389/fnana.2013.00025

ISSN=1662-5129

ABSTRACT=<p>Noise overexposure may induce permanent noise-induced hearing loss (NIHL). The cochlear nucleus complex (CNC) is the entry point for sensory information in the central auditory system. Impairments in gamma-aminobutyric acid (GABA)—mediated synaptic transmission in the CNC have been implicated in the pathogenesis of auditory disorders. However, the role of protein kinase C (PKC) signaling pathway in GABAergic inhibition in the CNC in NIHL remains elusive. Thus, we investigated the alterations of glutamic acid decarboxylase 67 (GAD67, the chemical marker for GABA-containing neurons), PKC γ subunit (PKCγ) and GABA<sub>B</sub> receptor (GABA<sub>B</sub>R) expression in the CNC using transgenic GAD67-green fluorescent protein (GFP) knock-in mice, BALB/c mice and C57 mice. Immunohistochemical results indicate that the GFP-labeled GABAergic neurons were distributed in the molecular layer (ML) and fusiform cell layer (FCL) of the dorsal cochlear nucleus (DCN). We found that 69.91% of the GFP-positive neurons in the DCN were immunopositive for both PKCγ and GABA<sub>B</sub>R1. The GAD67-positive terminals made contacts with PKCγ/GABA<sub>B</sub>R1 colocalized neurons. Then we measured the changes of auditory thresholds in mice after noise exposure for 2 weeks, and detected the GAD67, PKCγ, and GABA<sub>B</sub>R expression at mRNA and protein levels in the CNC. With noise over-exposure, there was a reduction in GABA<sub>B</sub>R accompanied by an increase in PKCγ expression, but no significant change in GAD67 expression. In summary, our results demonstrate that alterations in the expression of PKCγ and GABA<sub>B</sub>Rs may be involved in impairments in GABAergic inhibition within the CNC and the development of NIHL.</p>