The Impact of Noise Exposure on the Permeability of the Blood-Labyrinth' Barrier

Abstract

This project was undertaken to investigate changes to the permeability of the blood-labyrinth barrier (BLB) following noise exposure (24 hour exposure of 100dB (SPL), 8-16kHz), through use of systemically administered Evans Blue (EB) in C57BL/6 mice. As EB has not been used extensively to investigate the BLB, an optimisation phase was carried out on non-exposed mice. It was discovered that the best method was a slow, intravenous (femoral vein) administration of 1% EB. This was conducted with the aid of a syringe pump, which enabled the delivery of 200μL of EB over 2 minutes. Using this method and approach, permeability changes to the BLB were investigated at particular timepoints (0-48 hours) following noise! exposure. Slight changes were detected at both a regional and vascular level. These generally appeared biphasic in nature, with increased permeability detected around 0 and 18-24 hours following noise, but not at other timepoints (generally speaking). However, some concerns arose about the various factors that may implicate the EB technique, such as volume of EB administered and time of viewing sections. A supplementary pilot study was conducted to investigate this further. In summary, this project implies that there may be some dynamic changes to the permeability characteristics of the BLB following noise exposure. However, before this can be concluded with confidence, further work needs to be done to investigate the various factors that impact on the EB technique.