Fig. 2

Functional and synaptic damage caused by styrene exposure in the cochlea. A Graph show mean ABR threshold values (means ± SEM) for click stimuli indicating a hearing loss (of about 25 dB) after styrene treatment (n = 14 rats for each group; Student’s t test, p < 0.001). B Amplitude–intensity curves obtained by measuring amplitude of wave II of ABR click responses with decreased intensity (means ± SEM). Styrene treatment induces a significant decrease of wave II amplitude, confirming neuronal damage. C, D Images of surface preparations of the organ of Corti from control (C) and styrene-treated animals (D). The one row of inner hair cells (IHCs) and three rows of outer hair cells (OHCs) are stained with DAPI to visualize cell nuclei. CtBP2 puncta (red staining) indicate pre-synaptic contacts between the hair cells and afferent nerve fibers, stained with NF200 (in green). Scale bar: 20 μm. Significant differences between groups are indicate by asterisks (***p < 0.001)