The purpose of this study is to investigate the long-term effects of treatment with the
selective post-synaptic a1-adrenergic blocker terazosin on serial in a population of subjects
with defined pre-motor Parkinson's disease (PD) risks and abnormal imaging exams. Imaging
changes will be correlated to the presence and severity of motor and non-motor symptoms of
PD, measured by validated clinical scales and cardiac autonomic function tests.