Validation of a tracer kinetic model for the quantification of 5-HT2A receptors in human brain with [C-11]MDL 100,907

Rainer Hinz, Zubin Bhagwagar, Philip J. Cowen, Vincent Joseph Cunningham, Paul M. Grasby

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Abstract

The positron emission tomography ( PET) ligand [C-11] MDL 100,907 has previously been introduced to image the serotonin 2A (5-HT2A) receptor in human brain. The aim of this work was to contribute to the verification of the tracer kinetic modelling in human studies. Five healthy volunteers were scanned twice after intravenous bolus injection of approximately 370MBq [C-11] MDL 100,907 using dynamic PET. One scan was performed under baseline condition, the other scan commenced 90 mins after a single oral dose of 30mg of the antidepressant mirtazapine, which binds to the 5-HT2A receptor. There did not appear to be radiolabelled metabolites of [C-11] MDL 100,907 in human plasma, which are likely to cross the blood - brain barrier. Total volumes of distribution VD in 11 different brain regions were estimated using a reversible, two tissue, four rate constants compartment model with a variable fractional blood volume term and the metabolite- corrected plasma input function. There were no significant changes of the VD in the cerebellum between the baseline and the blocked scans confirming the cerebellum as a region devoid of displaceable binding. Regional estimates of binding potential were then obtained indirectly using the cerebellar VD and occupancies calculated. The mean occupancy with this clinically effective dose of mirtazapine was 60% without significant regional differences. This study confirmed the use of an arterial input kinetic model for the quantification of 5- HT2A receptor binding with [C-11] MDL 100,907 and the use of the cerebellum as a reference region for the free and nonspecific binding.

Original languageEnglish
Pages (from-to)161-172
Number of pages12
JournalJournal of Cerebral Blood Flow and Metabolism
Volume27
Issue number1
Early online date10 May 2006
DOIs
Publication statusPublished - Jan 2007

Keywords

  • [11C]MDL 100,907
  • 5-HT2A receptors
  • human brain
  • mirtazapine
  • positron emission tomography
  • tracer kinetic modelling
  • positron-emission-tomography
  • injection pet data
  • F-18 altanserin
  • rat-brain
  • radiolabeled metabolites
  • C-11 MDL-100907
  • messenger-RNA
  • radioligand
  • depression
  • serotonin

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