Motor Response to Sildenafil in PD

Erectile dysfunction can be experienced by up tp 40% of men with Parkinsons Disease (PD). Sildenafil (Viagra(R))is widely used by men with PD and erectile dysfunction. A number of patients have reported that when they take Sildenafil, their need of anti-PD medication is reduced. We hypotheses that sildenafil increases cerebral blood flow in basal ganglia and hence improves the function, improving motor function. Motor function and cerebral blood flow (rCBF) of 8 patients will be tested before and after Sildenafil intake and before and after anti-PD medication. rCBF will be measured by the Xe133 inhalation method and a fast-rotating, brain-dedicated, single photon emission computerized tomograph (SPECT, Tomomatic, 232, Medimatic, Inc., Denmark). Two scans will be perfomed, when patients are i)in normal medicated state and ii) in normal medicated state 1 hour after intake of 100 mg sildenafil. Motor function will be measured i 4 conditions: i)in normal medicated state and ii) in normal medicated state 1 hour after intake of 100 mg sildenafil, iii) after 12 hours of discontiation of anti-PD mediciation and iiii) after 14 hours of discontiation of anti-PD mediciation and 1 hour after intake of 100 mg sildenafil.