Relationship between central and peripheral serotonin 5-HT2A receptors: a positron emission tomography study in healthy individuals.

5-HT2A receptors on platelet membranes are often measured as indirect markers of the central 5-HT2A receptors. However, the 5-HT2A receptors on the platelets and those in the brain have never been assessed simultaneously in humans. The purpose of this study was to evaluate the relationship between platelet membrane and neocortical 5-HT2A receptors measured simultaneously in normal healthy volunteers. Twelve healthy volunteers had the 5-HT2A receptors on their platelet membranes assessed in vitro using [3H]lysergic acid diethylamide ([3H]LSD) and their central 5-HT2A receptors measured in vivo using [18F]setoperone and positron emission tomography (PET) imaging. We find no significant correlation between the binding potential (Bmax/Kd) of 5-HT2A receptors on platelets and in brain in the same individual (F1,10 = 0.7, P = 0.42). The study was limited by a small sample and the fact the two different ligands were used (i.e. LSD for platelets and setoperone for brain); nonetheless, the findings suggest that changes in platelet 5-HT2A receptors may not indicate similar changes in central 5-HT2A receptors.