A PET study of brain 5-HT2 receptors and their correlation with platelet 5-HT2 receptors in healthy humans

Rationale: Platelets share many properties with brain serotonergic neurons such as active 5-hydroxytryptamine (5-HT) transport, 5-HT2 receptors, and m itochondrial monoamine oxidase. Objectives. We measured brain 5-HT2 recepto rs and platelet 5-HT2 receptors in healthy volunteers to determine if there was any correlation between the two measures. Methods: Ten healthy volunte ers with no lifetime history of psychiatric illness or family history in fi rst-degree relatives were recruited, 5-HT2 receptor binding was determined for each subject with positron emission tomography and [F-18]setoperone sca n in the brain and with H-3-LSD binding in platelets. Results. We found no significant correlation between 5-HT2 binding potential (BP) in platelets ( B-max/K-d) and a semiquantitative estimate of 5-HT2 BP in frontal, parietal , and temporal cortical regions. SPM voxel based analysis also showed no si gnificant correlation between the 5-HT2 BP in platelets and in the brains o f the study subjects. Conclusions: Brain 5-HT2 receptor binding was not sig nificantly correlated to platelet 3H-LSD binding in healthy subjects. This raises questions about the validity of generalizing findings from platelet studies to 5-HT neurons in the brain.