Blood pressure responses to noradrenaline and dopamine infusions in Parkinson's disease and the Shy-Drager syndrome.

Studies of pulse rate and blood pressure responses to graded intravenous infusions of noradrenaline and dopamine were performed on five patients with Parkinson's disease, five with the Shy-Drager syndrome and seven healthy subject. Cardiovascular reflex responses to standing and to the Valsalva manoeuvre were found to be preserved in all patients with Parkinson's disease but to be grossly defective or absent in all with the Shy-Drager syndrome. Each subject received separate intravenous infusions of L-noradrenaline and dopamine, delivered at increasing rates, until a 30% rise in systolic blood pressure was achieved. Heart rate decreased during pressor responses to noradrenaline in control subjects and patients with Parkinson's disease, but increased in those with the Shy-Drager syndrome. Heart rate increased during pressor responses to dopamine in all subjects. Compared to control subjects supersensitivity to noradrenaline was observed both in patients with Parkinson's disease and, to a greater extent, in those with the Shy-Drager syndrome. Subsensitivity to dopamine was observed in patients with Parkinson's disease, but supersensitivity in those with the Shy-Drager syndrome.