Dynamics of noise induced neurodegeneration and neuroplasticity in the central nervous system

Noise induced hearing loss (NIHL) has a strong impact on the peripheral auditory system, but it could also induce neurodegenerative and neuroplastic changes within key regions of the central nervous system (CNS). The present study investigated how cell density, axonal density and glutamatergic and GABAergic neurotransmission are affected at different time points as a consequence of noise exposure in two core regions of the central auditory pathway: the central inferior colliculus (ICc) and the ventral medial geniculate body of the thalamus (vMGB). Mice were noise-exposed during 3 h at 115 dB and 90 dB sound pressure level (SPL) (5–20 kHz) and were separately investigated in different timepoints after noise exposure: 1 day, 7 days, 56 days and 84 days. Unexposed mice were used as control. Voxel-Based Morphometry (VBM), Difussion Tensor Imaging (DTI) and 1H Magnetic Resonance Spectroscopy (1H-MRS) techniques using 7T magnetic resonance imaging (MRI) were performed on the corresponding timepoint and frequency-specific auditory brainstem responses (ABR) were recorded to examine auditory thresholds. Afterwards, fluorescence immunohistochemistry techniques were used to assess neuronal and cellular density (NeuN and DAPI), neurofilament density (SMI312) and glutamatergic and GABAergic imbalances (VGLUT1, VGLUT2 and VGAT). Present findings suggest that ABR thresholds were significantly elevated in exposed animals when compared to controls. Furthermore, MRI and histological data showed complex neurodegenerative and neuroplastic fluctuations as a consequence of NIHL. These results suggest complex adaptative mechanisms present in the auditory CNS structures as a consequence of acute overstimulation. Project supported by the Deutsche Forschungsgemeinschaft (GR3519/4-1, BO4484/2-1).

Publication History

Article published online:
12 May 2023