9309856 Jordan During normal development, adult patterns of synaptic connections are established through an elimination of excess neural connections. For example, in newborns, muscle fibers receive innervation from several different motoneurons. By the time the mammal has matured into adulthood, muscle fibers are each typically innervated by only a single motoneuron. Dr. Jordan's research program seeks to understand the cellular and molecular bases of synapse elimination. Her model is a a relatively simple neuromuscular system, namely the perineal levator ani muscle and its innervating motoneurons located in the spinal nucleus of the bulbocavernosus. Studying synapse elimination in this system offers the significant advantage that this mechanism can be regulated by steroid hormones. Androgen treatment during a specified period of development permanently prevents some synapse elimination in this system. Thus, androgens are a naturally occurring factor that influences the development of the central nervous system. Dr. Jordan will use steroid hormones as a tool for the control and manipulation of synapse elimination. Information about where androgen acts to prevent this loss is necessary for directing further experiments aimed at identifying the underlying mechanisms. In addition, she will examine the mechanisms that initiate the onset of synapse elimination. Dr. Jordan will explore the possibility that it is the electrical uncoupling of the neurons that underlie the selective stabilization and maintenance of synapses. Information gained about the factors controlling this crucial developmental event in the neuromuscular system could be applied to neuronal populations in the brain that undergo similar synaptic alternations due to either normal or pathological processes. ***
