No change in [ 11 C]CUMI‐101 binding to 5‐HT 1A receptors after intravenous citalopram in human

The main objective of this study was to determine the sensitivity of [ 11 C]CUMI‐101 to citalopram challenge aiming at increasing extracellular 5‐HT. CUMI‐101 has agonistic properties in human embryonic kidney 293 cells transfected with human recombinant 5‐HT 1A receptors (Hendry et al. [2011] Nucl Med Biol 38:273–277; Kumar et al. [2006] J Med Chem 49:125–134) and has previously been demonstrated to be sensitive to bolus citalopram in monkeys (Milak et al. [2011] J Cereb Blood Flow Metab 31:243–249). We studied six healthy individuals. Two PET‐scans were performed on the same day in each individual before and after constant infusion of citalopram (0.15 mg/kg). The imaging data were analyzed using two tissue compartment kinetic modeling with metabolite corrected arterial input and Simplified Reference Tissue Modeling using cerebellum as a reference region. There was no significant difference in regional distribution volume or non‐displaceable binding potential values before and after citalopram infusion. The mean receptor occupancy was 0.03 (range −0.14 to 0.17). Our data imply that [ 11 C]CUMI‐101 binding is not sensitive to citalopram infusion in humans. Synapse, 2012. © 2012 Wiley Periodicals, Inc.