This investigation examines the effects of tranylcypromine on the uptake, release, and metabolism of intracisternally administered tritiated norepinephrine (norepinephrine-H3) in rat brain. The findings suggest that, in addition to being a potent inhibitor of the enzyme monoamine oxidase, tranylcypromine discharges norepinephrine extraneuronally onto receptors and possibly also inhibits the neuronal reuptake of this amine. These neuropharmacological effects of tranylcypromine may possibly account for the greater clinical efficacy of tranylcypromine in the treatment of some depressed patients and the higher incidence of hypertensive cerebrovascular reactions when this drug is compared with other monoamine oxidase inhibitors.Abstract Teaser