Human brain cortex and platelet serotonin 2 receptor binding properties and their regulation by endogenous serotonin

Abstract

In patients with affective disorder and suicidality up-regulation of the serotonin 2 receptor has been observed in brain and on platelets. Although the pharmacological profiles of the receptor in brain synaptosomes and platelet membranes are similar, it is a matter of debate whether the platelet serotonin 2 receptor reflects the characteristics of the receptor in the brain and whether serotonin regulates the receptor activity. To answer these questions we measured in healthy human subjects the platelet serotonin 2 receptor activity and blood serotonin concentrations. In an attempt to find whether the serotonin 2 receptor activity in brain cortex synaptosomes and on platelets is similarly expressed we investigated the receptor's binding characteristics in neurosurgical patients. The results suggest that in men and women increased platelet serotonin concentrations correlate with a decrease in platelet membrane serotonin 2 receptor affinity. The affinities of the brain cortex synaptosomal and platelet membrane serotonin 2 receptor correlate intra-individually. These data suggest that the platelet serotonin 2 receptor affinity appears to be regulated at the cellular level by blood serotonin and that the binding characteristics of the serotonin 2 receptor in brain cortex synaptosomes corresponds to that on platelets. The latter finding supports the hypothesis of the platelet as a model for neuronal function.