9421448 Forehand Homeostasis is the process by which the body maintains temperature, blood pressure, digestion, and a variety of other physiological functions necessary for life. Homeostasis is controlled unconsciously through connections of the autonomic nervous system. Control centers in the brainstem regulate organ function via their connections with neurons in the spinal cord and peripheral ganglia. It is clear that optimum organ function can be achieved only by a fine matching of command neurons with their targets, yet it is unclear how cells in the developing autonomic nervous system convey to one another critical information about their position and destinations. Recent studies have begun to elucidate the organization of embryonic preganglionic thoracic neurons into discrete groups of cells. These neurons are located in the spinal cord and send information from the brain to a series of autonomic ganglia via processes called axons. This research is designed to determine how these axons find the appropriate autonomic ganglia so that the message is received by the correct ganglion cells. Preganglionic axons must contact a number of ganglia located at the rostral end of the body (towards the head) or at the caudal end of the body (towards the tail or feet). Some preganglionic axons project rostrally and others project caudally; no axon splits to project in both directions. The immediate goal of the proposed research is to determine the way in which these axons make this choice. One set of experiments will determine the way in which the appropriate numbers of axons that are to project in each direction are established. In other experiments, the way in which the axons bundle together to project to the ganglia will be examined to determine if axons destined to project one direction selectively bundle with like axons. The results of these experiments will elucidate factors that lend a unique identity to individual pools of preganglionic neurons. Ultima tely, this research will define functional cell groups of the preganglionic cell column relative to their topographic targets and the organs they regulate. This experimental paradigm has the potential to provide a unique situation for studying the general way in which topographic maps of the body are matched to various levels of the nervous system .
