Effect of the beta-2 adrenergic agonist zinterol on norepinephrine turnover

Acute treatment with the beta-2 adrenergic agonist zinterol increased norepinephrine (NE) turnover in cerebral cortex and hypothalamus as measured by the rate of disappearance of NE after treatment with alpha-methyl-p- tyrosine. With repeated treatment, zinterol no longer increased NE turnover in hypothalamus; in cerebral cortex, its effect after repeated treatment was diminished relative to its acute effect. Repeated treatment with zinterol also reduced NE levels and turnover in cardiac ventricles. The present results suggest that zinterol may exert presynaptic actions on noradrenergic neurons in the central and peripheral nervous systems.