Central and peripheral auditory abnormalities in chinchilla animal model of blast-injury

•Repeated moderate blast exposures result in both central and peripheral auditory abnormalities as indicated by changes in auditory brainstem responses, tympanic membrane damage and different degree of changes in neurotransmitter receptors in brain regions that are known to contribute to sensory auditory information processing.•Blast can cause a direct effect on the central auditory system due to direct transmission.•In the blast, changes to CAS may be affected both directly from shock as well as damage from the peripheral system.•Though earplugs protect inner/middle ears, they do not protect CAS.•Therefore, targeting central neurotransmitter abnormalities may have a therapeutic benefit to restore the central auditory system and attenuate blast-induced tinnitus/hearing loss. Exposure to blast overpressure or high-intensity sound can cause injuries to the auditory system, which leads to hearing loss or tinnitus. In this study, we examined the involvement of peripheral auditory system (PAS), and central auditory system (CAS) changes after exposure to blast overpressure (15-25 psi) on Day 1 and additionally during 7 days of post blast time period in chinchillas. Auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), and cochlear hair cell changes were measured or identified in post-blast period within 7 days to detect injuries in the PAS. In the CAS, changes in NMDAR1 (excitatory receptor) and GABAA (inhibitory receptor) as well as changes in serotonin (5-HT2A) and acetylcholine (AChR) receptors were examined in different brain regions: auditory cortex (AC), geniculate body (GB), inferior colliculus (IC) and amygdala by immunofluorescence staining. We observed the PAS abnormalities of increased ABR threshold and decreased DPOAE response in animals after blast exposure with hearing protection devices (e.g., earplug). Blast exposure also caused a reduction in both NMDAR1 and GABAA receptor levels in acute condition (post-blast or Day 1) in AC and IC, while serotonin and acetylcholine receptor levels displayed a biphasic response at Day 1 and Day 7 post-exposure. Results demonstrate that the earplug can protect the tympanic membrane and middle ear against structural damage, but the hearing level, cochlear outer hair cell, and the central auditory system (levels of excitatory and inhibitory neurotransmitter receptors) were only partially protected at the tested blast overpressure level. The findings in this study indicate that blast e