title: Noise-induced damage to ribbon synapses without permanent threshold shifts in neonatal mice.
abstract: Recently, ribbon synapses to the hair cells (HCs) in the cochlea have become a novel site of interest in the investigation of noise-induced cochlear lesions in adult rodents (Kujawa and Liberman, 2009; Lin et al., 2011; Liu et al., 2012; Shi et al., 2013). Permanent noise-induced damage to this type of synapse can result in subsequent degeneration of spiral ganglion neurons (SGNs) in the absence of permanent changes to hearing sensitivity. To verify whether noise exposure during an early developmental period produces a similar impact on ribbon synapses, the present study examined the damaging effects of noise exposure in neonatal Kunming mice. The animals received exposure to broadband noise at 105-decibel (dB) sound pressure level (SPL) for 2h on either postnatal day 10 (P10d) or postnatal day 14 (P14d), and then hearing function (based on the auditory brainstem response (ABR)) and cochlear morphology were evaluated during either postnatal weeks 3-4 (P4w) or postnatal weeks 7-8 (P8w). There were no significant differences in the hearing threshold between noise-exposed and control animals, which suggests that noise did not cause permanent loss of hearing sensitivity. However, noise exposure did produce a significant loss of ribbon synapses, particularly in P14d mice, which continued to increase from P4w to P8w. Additionally, a corresponding reduction in the amplitude of compound action potential (CAP) was observed in the noise-exposed groups at P4w and P8w, and the CAP latency was elongated, indicating a change in synaptic function.
authors.affiliation: Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China. Electronic address: shilj_seu@163.com.
authors.forename: L
authors.initials: L
authors.lastname: Shi
authors.affiliation: Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China; Children's Medical Center, The Second Affiliated Hospital of Nanjing Medical University, 262 Zhongshan Road North, Nanjing 210003, China. Electronic address: guoxiaojing0818@126.com.
authors.forename: X
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China. Electronic address: spei1020@sina.cn.
authors.forename: P
authors.initials: P
authors.lastname: Shen
authors.affiliation: Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China. Electronic address: liulj321@163.com.
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China. Electronic address: 695377378@qq.com.
authors.forename: S
authors.initials: S
authors.lastname: Tao
authors.affiliation: Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China. Electronic address: lixiaowei6138@126.com.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Otolaryngology, 6th Affiliated Hospital, Jiaotong University, 600 Yishan Road, Shanghai 200233, China. Electronic address: 13816506336@126.com.
authors.forename: Q
authors.initials: Q
authors.lastname: Song
authors.affiliation: School of Human Communication Disorders, Dalhousie University, 1256 Barrington Street, Halifax, NS B3J1Y6, Canada. Electronic address: zyu@dal.ca.
authors.forename: Z
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Department of Otolaryngology, 6th Affiliated Hospital, Jiaotong University, 600 Yishan Road, Shanghai 200233, China. Electronic address: yinshankai@china.com.
authors.forename: S
authors.initials: S
authors.lastname: Yin
authors.affiliation: Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China; School of Human Communication Disorders, Dalhousie University, 1256 Barrington Street, Halifax, NS B3J1Y6, Canada. Electronic address: Jian.Wang@dal.ca.
authors.forename: J
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D003051:Cochlea / Q000473:pathology* / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D051379:Mice; D011897:Random Allocation; D013569:Synapses / Q000473:pathology* / Q000502:physiology*
keywords: cochlea; neonatal mice; noise; permanent threshold shift; ribbon synapse