The human platelet as a pharmacologic model for the adrenergic neuron

The uptake of norepinephrine (NE) by the human platelet resembles that of the adrenergic neuron. Platelets incubated with d1‐ 14 C‐NE (2.1 x 10 −6 M) for one hour at 37° C. concentrated the amine to a distribution ratio of 5.1 ± 0.1. Uptake was markedly reduced by cold and metabolic inhibitors such as cyanide, fluoride, dinitrophenol, and PCMB. NE uptake was also diminished by ouabain, quinidine, and substitution of lithium for sodium in the medium, suggesting the uptake mechanism is related to a sodium pump. Drugs which interfere with the uptake of NE by the neuron have a similar effect on the platelet. Uptake of 14 C‐NE was impaired by serotonin (5HT), tryptamine, tyramine, amphetamine, bretylium, debrisoquin, guanethidine, desmethylimipramine, and various antihistamines. 14 C‐NE accumulated in the platelet by a preliminary incubation was released by reserpine, tyramine, phenylephrine, and debrisoquin, less by guanethidine, but not by ephedrine or mephentermine. 14 C‐5HT was released by reserpine, tyramine, debrisoquin, and mephentermine, less by ephedrine, but not by guanethidine or phenylephrine. Thus, release or failure of release of NE or 5HT from platelets will not necessarily reflect the action of a drug on sympathetic neurons.