The peripheral kinetics of norepinephrine in depressive illness.

Sympathetic nervous system function was studied in patients with primary depressive illness. Tritiated norepinephrine was used to measure the rate of entry to plasma of norepinephrine released from sympathetic nerves ("norepinephrine spillover rate"), and to assess the neuronal uptake of norepinephrine by studying the removal of norepinephrine from plasma. Norepinephrine spillover was elevated in five of 11 patients. This abnormality, which was unrelated to the presence of individual vegetative symptoms, occurred exclusively in patients with endogenous depression. The rapid-removal phase of the disappearance of tritiated norepinephrine from plasma, which seemed to correspond with neuronal uptake of norepinephrine, was accelerated in patients with depressive illness, providing presumptive evidence of increased neuronal uptake. If norepinephrine uptake is also accentuated within the brain, a functional deficiency of the transmitter at adrenergic receptor sites might result.