New techniques of nerve tissue culture allow preparations in which, a) axons of specific neuronal types are grown free of supporting cells, b) synapses are formed on identified cell types in dissociated cell cultures, and c) Schwann cells are available in "pure" culture free of other cell types. These permit experimental access to membrane surfaces not available in vivo. By applying the techniques of 125I surface labelling, SDS polyacrylamide gel electrophoresis, and lectin binding as well as electron microscopy to these preparations, we propose to compare: a) surface components of axons of autonomic neurons, sensory neurons and spinal cord outgrowth to see if these components can be shown to differ between neuronal types, and b) whether these surface components are characteristic for neuronal type from species to species (rat, mouse, chick). Combining study of "naked" sensory neurites with studies of Schwann cell populations we will attempt to determine, a) if a new axonal surface component appears at the time the sensory axon matures to the point of inducing myelin formation, and b) when typical peripheral myelin proteins appear in the maturation of the Schwann cell. Utilizing the availability of "pure" Schwann cell populations we will test, a) whether these are able to relate to (and guide) CNS axons in tissue culture, and b) whether Schwann, neuroglial or ependymal cell "bridges" are useful in promoting recovery after spinal cord transection in the rat.