9421695 William F. Collins The ability of the central nervous system cells to reconfigure their structure and contacts as result of environmental or chemical queues is paramount to learning, memory, behavior and brain function, in general. Reconstruction occurring in the central nervous system is defined as plasticity. Moreover, the impact of gonadal hormones, such as androgens, on brain structure and function is only beginning to become evident. However, other studies suggest that these powerful hormones are essential for the normal function of neurons and their loss results in atrophy and cell loss. Dr. Collins will use a well-characterized motoneuron model system to explore the anatomical and electrophysiological consequences of gonadal androgen deficiency on central nervous system motoneurons. Initially, Dr. Collins will assess the electrophysiological properties of motoneurons and their anatomical structure before and after androgen withdrawal, in some cases up to 6 months after the last exposure to androgens. Specifically, androgen dependence among dendrites will be examined. Finally, Dr. Collins will examine the efficacy of synaptic inputs to the identified motoneurons by electrically driving presynaptic cells and assess their post-synaptic influence in the presence or absence of androgens. These studies will reveal novel mechanisms of steroid hormone action on brain motoneurons and begin to elucidate mechanisms of androgen-dependent neuron plasticity. While little is understood about the role of neural plasticity in brain function, gonadal steroid hormones are effective in their ability to reorganize the critical brain centers that may be essential for such critical tasks as learning and memory in man and all species alike.
