Shape change and uptake of 5-hydroxytryptamine in human blood platelets: action of neuropsychotropic drugs.

Psychotropic drugs acted as agonists, antagonists or mixed agonists-antagonists of the shape change mediated by the 5HT receptor in blood platelets of man incubated in a protein-poor medium. Regarding inhibition of 5HT uptake some of the drugs were equally potent in both reserpinized and normal platelets, whereas others showed lower or higher potencies in the former than in the latter. There was no correlation between the potencies of the drugs as shape change inhibitors and as uptake inhibitors. It is concluded that 1) human platelets may serve as models for the neuronal 5HT receptors of some areas of the central nervous system, 2) platelets can be used to determine the subcellular site of action of 5HT uptake inhibitors and 3) the receptors responsible of the shape change, and the site of the 5HT transport at the plasma membrane are different entities.