The growth of intersegmental pathways will be examined at early developmental stages in the chick embryo spinal cord. Retrograde and anterograde labeling of growth cones and pathways will be carried out using HRP histochemistry and the material examined in the light and electron microscope. The localization of several molecules that may be involved in axonal guidance and pathway formation will be examined by immunocytochemistry. A variety of perturbation experiments, including deletion of specific pathways or pathways cues, heterotopic spinal cord transplants, spinal cord rotations, and supression of neuronal activity will be used to begin to reveal some of the possible mechanisms involved in pathway formation. The long-term goal of these studies is to gain a better understanding of the cellular and molecular mechanisms that are critically involved in the ontogeny of specific axonal pathways in the vertebrate spinal cord. Understanding the mechanisms that regulate pathway formation during development is directly relevant to the important topics of spinal cord regeneration and related forms of neuronal plasticity.
