A central issue in developmental neuroscience concerns the mechanisms underlying the development of specific connections between two nerve cells. Fundamental to the formation of these connections is the guidance of axons along specific pathways to reach their target cells. In the sympathetic nervous system, preganglionic nerve cells send information from the brain and spinal cord to cells located in sympathetic ganglia. The ganglia relay this information to the heart, blood vessels, and glands. The way in which preganglionic nerve cells are able to find the ganglion during development will be investigated. The path will be identified by marking nerve cells in the rat and chicken embryo with a dye that permits the visualization of the earliest fibers growing out from these nerve cells. The time and way in which the specific projection pathways are chosen by preganglionic neurons will be described. These studies promise to provide a basis for future investigations into the mechanisms involved in directing the guidance of axons in the mammalian sympathetic nervous system.
