Catecholamine-containing neurones participate in cardiovascular regulation not only through the peripheral sympathetic nervous system but also by central nervous adrenergic mechanisms. Impairment of peripheral sympathetic activity leads to baroreflex impairment and postural hypotension. While changes in central function may alter baroreflex sensitivity, supine hypotension with preservation of postural compensation is more common. Levodopa has been demonstrated to exert both central and peripheral effects on blood pressure in parkinsonian patients.