The effects of dopamine agonists on human cardiovascular and sympathetic nervous systems.

We gave people four different dopamine agonists and monitored blood pressure, heart rate and circulating catecholamine levels. Bromocriptine decreased blood pressure and plasma norepinephrine levels. Dopamine increased pulse pressure, heart rate and circulating epinephrine (E) and norepinephrine (NE) levels. Dopamine agonists tend to diminish blood pressure by inhibiting sympathetic neuronal discharge of NE and, to a lesser extent, by stimulating dopamine vascular receptors. However, dopamine and L-dopa can be converted to NE and E, both of which have pressor effects. The complex cardiovascular effects of dopamine agonists are the result of stimulation of dopamine vascular and neuronal receptors and the production of NE and E.