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Upregulation of the Platelet Serotonin2A Receptor and Low Blood Serotonin in Suicidal Psychiatric Patients

Suicidality has been found to be associated with low pre- and postsynaptic serotonin functioning. The purpose of this study was to examine whether in acutely suicidal psychiatric inpatients, the blood serotonin concentration was related to the underlying psychiatric disorder and whether it was associated with changes in the affinity (dissociation constant, KD) or in the maximal binding capacity (Bmax) of the platelet serotonin2A receptor. We therefore determined the blood serotonin concentrations and the platelet serotonin2A receptor activities of 45 suicidal psychiatric patients and 20 healthy subjects. We found that the blood serotonin concentrations were significantly lower in suicidal patients compared to healthy subjects. In all diagnostic categories (affective disorder, schizophrenia and adjustment disorder) we noted a significantly higher maximal binding capacity of the platelet serotonin2A receptor. These findings support the notion that a reduction in the availability of serotonin and an upregulation of the serotonin2A receptors in psychiatric patients are associated with a loss of control over suicidal impulses.