A new model for investigating hair cell degeneration in the guinea pig following damage of the stria vascularis using a photochemical reaction

We have established a new model for investigating the relationship between cochlear lateral wall damage and sensory cell degeneration in guinea pigs by using a photochemical reaction between the systemic injection of Rose Bengal (RB) and controlled green light irradiation to the cochlea. The photochemical reaction produced a reactive oxygen species, which then damaged the endothelium. This triggered platelet adhesion and aggregation at the site of endothelial injury to produce thrombi and affect microcirculation in the lateral wall at the site of irradiation. Changes were studied under a scanning electron microscope (SEM), and compound action potentials (CAP) were measured. SEM observations after tangential illumination of the cochlear wall revealed degeneration of the stria vascularis (SV). Specific morphological findings at 24 h included delayed degeneration of the outer hair cells concurrent with a significant increase in the CAP. Based on these findings, we suggest that degeneration of the SV was a direct result of the photochemical reaction, but CAP changes and sensory hair cell damage were secondarily caused by SV degeneration.