Platelet 5-hydroxytryptamine accumulation in depressive illness.

The uptake of 5-hydroxytryptamine (5-HT) by blood platelets from controls, depressed patients and recovered depressed patients has been determined using short incubation times and low substrate concentrations. The affinity of serotonin for the platelet membrane appears to be normal in acutely depressed and recovered depressed patients. The capacity of transport of 5-HT through the platelet membrane is impaired in these depressive patients and this impairment is independent of the psychiatric status of the patients and is discussed in the light of the electrolyte and enzyme disturbances that are associated with depressive illness.