Platelet serotonin in essential hypertension and in mental depression.

The similarity between the metabolic pathways of serotonin in platelets and serotoninergic nerve endings has often been emphasized. The turnover of serotonin was therefore investigated in two diseases: hypertension (as central serotoninergic neurones appear to modulate central sympathetic nervous activity) and depression (as a central 5-HT-deficiency and a low 3H-imipramine binding on platelets have been described in patients with endogenous depression). Mean platelet 5-HT level was significantly lower in essential hypertensives than in controls. A reduction in platelet 5-HT level was also observed in depression and was more marked in women than in men. Serotonin level was only weakly related to the severity of the diseases. In some hypertensive patients, administration of ketanserin resulted in a reduction of blood pressure without affecting 5-HT level. In depressive patients, maprotiline and chlorimipramine acted differently on 5-HT level but both improved the clinical symptoms.