Whole-mount procedures for simultaneous visualization of nerves, neurons, cartilage and bone

Herein are described two techniques to selectively label and/or stain afferent and efferent fibers and their cell bodies and simultaneously stain bone and cartilage. One technique uses anti-acetylated alpha-tubulin immunohistochemistry to follow the course, peripheral branching, and origin of the ventral spinal nerve innervating the axial musculature and a second uses anterograde and retrograde transport of selectively applied 3 kDa biotin dextran amines to identify specific afferent and efferent projections and their cell bodies. Both procedures can be combined with an enzyme clearing and staining procedure for the simultaneous visualization of bone (alizarin red S) and cartilage (alcian blue) in whole-mount preparations. Myelinated and unmyelinated nerve fibers are stained dark brown with the 3,3' diaminobenzidine tetrahydrochloride (DAB) reaction product, whereas cartilage is stained blue (alcian blue) and bone is red (alizarin red S). The combination of these procedures provides a simultaneous three-dimensional understanding of the topography of afferent and efferent projections and their cell bodies and the axial and appendicular skeletal system, which is key to understanding the compartmental relationships of the spinal cord with respect to the axial and appendicular skeleton.