Figure 7.

Cochlear effects of activating the medial olivocochlear efferents are undiminished by deletion of mAChR receptors. To assay efferent effects, DPOAE amplitudes evoked by low-level tones are measured before, during, and after delivering a 70 s shock train to the olivocochlear bundle at the floor of the IVth ventricle. A, One run of the assay for each mAChR knock-out shows DPOAE amplitudes, normalized to the mean pre-shock value. Efferent effect is defined as the difference between the pre-shock mean and the mean DPOAE amplitude for the first three measures taken after shock-train onset (i.e., during shock window). B, Mean ± SEM efferent effect size for wild-type versus mAChR-null ears for each of the four lines tested.