An in vitro preparation to access cellular and neuronal components in the mouse inner ear

An in vitro mouse temporal bone preparation has been developed in order to allow the investigation of structures and functions in a living hearing organ. Fluorescent vital probes (a potentiometric styryl dye, RH 795, and a vital dye staining cellular cytoplasm, calcein) were perfused through the scala tympani to stain cellular components of the cochlea. Observations of the cochlear apical turn were performed using a confocal microscope. In spite of the anatomical constraints due to the small size of the mouse cochlea, detailed images were obtained. The sensory cells as well as their innervating nerve fibres were clearly seen. Nerve fibres crossing the tunnel of Corti and projecting to the outer hair cells could also be visualised.