A, auditory brainstem responses. Left panel: mean ABR traces of non-injected (black) and Syt1-AAV injected (grey) ears of Otof+/− animals (n = 4) in response to 80 dB SPL; right panel, mean ABR traces of Otof−/− animals of which one ear was transfected with Syt1 (grey) and the non-injected contralateral ear served as control (black, n = 4) in response to 100 dB SPL.
B, left panel: mean ABR thresholds and standard errors (sem, n = 25) of non-injected and eGFP-transfected wild type animals (C57B6J). Right panel: mean ABR thresholds and sem (n = 4) of non-injected and Syt1-transfected Otof+/− mice. In both independent sets of virus transduction, no ABR response could be detected in non-injected and in Syt1-transfected Otof−/− mice for sound pressure levels (SPL) up to 120 dB (n = 29).
C, outer hair cell function was confirmed by DPOAEs for Otof+/− and Otof−/− mice (same animals as in right panel of B). While in Otof+/− mice the DPOAEs were slightly worse after virus injection (left panel) and might be a reason for the slightly elevated ABR thresholds in B, DPOAEs in Otof−/− seem not to be affected by virus transduction (right panel).