Whole-Mount Dissection of the Vestibular Complex and Quantification of Vestibular Ganglion Neurons in Mice.

The vestibular system is crucial for our sense of balance, for detecting head movements, and for regulating gaze and posture. There are five vestibular organs located inside the temporal bone, including two otolith organs (utricle and saccule), which detect linear movement, and three cristae (lateral/horizontal, anterior, and posterior), which detect rotational movement. Each organ contains a sensory epithelium with hair cells that detect head movements and supporting cells that provide structural support, release growth factors and cytokines, and phagocytose dying hair cells. The neurons that make synapses with hair cells project from the vestibular ganglion (also called Scarpa's ganglion), which is located on the surface of the temporal bone. Most previous studies of the vestibular ganglion have used sectioning methods to visualize these cells, which have several limitations. Here, we describe a method to dissect the mouse vestibular ganglion and its connecting organs (saccule, utricle, and three cristae) as a whole mount, enabling more detailed analysis of neuronal cell bodies and their dendritic projections to the sensory epithelia. These methods include fixation, decalcification, dissection, immunofluorescent staining, confocal imaging, and three-dimensional quantification of vestibular neurons.