Immunohistochemistry localises myosin-7a to cochlear efferent boutons

Myosin 7a is often used to visualise sensory hair cells due to its well-characterised and localised expression profile. We thus conducted myosin-7a immunostaining across all 3 turns of the adult rat organ of Corti to visualise hair cells. As expected, we observed myosin 7a staining in both inner and outer hair cells. Unexpectedly, we also observed strong myosin 7a staining in the medial olivocochlear efferent synaptic boutons contacting the outer hair cells. Efferent bouton myosin-7a staining was present across all 3 turns of the cochlea. We verified this localisation by co-staining with a known efferent bouton marker, the vesicular acetylcholine transporter.Â