5-Hydroxytryptamine in platelets of torsion dystonia patients.

In an effort to explore possible changes in 5-hydroxytryptamine (5-HT) metabolism in idiopathic torsion dystonia (ITD), platelets from patients were studied. Platelet 5-HT concentrations did not differ from those in matched controls. 5-HT uptake by the platelets was also studied, and the results demonstrated significantly higher Km values, but Vmax values were normal among patients. Inhibition by imipramine of 5-HT uptake by platelets taken from ITD patients was also normal. The therapeutic implications of the low affinity of 5-HT to its platelet receptors are discussed.