title: SPECT measurement of benzodiazepine receptors in human brain with iodine-123-iomazenil: kinetic and equilibrium paradigms.
abstract: Iodine-123-iomazenil binding to benzodiazepine receptors in human brain was measured with SPECT using kinetic and equilibrium methods.
  
  
  METHODS
  In the kinetic experiments (n = 6), regional time-activity curves after a single bolus injection of the tracer were fit to a three-compartment model to provide estimates of the rate constants K1 to k4. The binding potential (equal to the product of the receptor density and affinity) was derived from the rate constants. In the equilibrium method (n = 8), the tracer bolus injection was followed by a constant tracer infusion to induce a sustained equilibrium state. The regional equilibrium volume of distribution was calculated as the ratio of the regional brain concentration-to-the free parent tracer steady-state plasma concentration. In three experiments, a receptor-saturating dose of flumazenil was injected for direct measurement of the nondisplaceable compartment distribution volume.
  
  
  RESULTS
  The kinetic and equilibrium method results were in good agreement in all regions investigated. Iodine-125-iomazenil binding potential measured in vitro in 12 postmortem samples was found to be consistent with SPECT in vivo measurements.
  
  
  CONCLUSIONS
  These studies demonstrated the feasibility of quantification of receptor binding with SPECT.
authors.affiliation: Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut.
authors.forename: A
authors.initials: A
authors.lastname: Abi-Dargham
authors.forename: M
authors.initials: M
authors.lastname: Laruelle
authors.forename: J
authors.initials: J
authors.lastname: Seibyl
authors.forename: Z
authors.initials: Z
authors.lastname: Rattner
authors.forename: R M
authors.initials: RM
authors.lastname: Baldwin
authors.forename: S S
authors.initials: SS
authors.lastname: Zoghbi
authors.forename: Y
authors.initials: Y
authors.lastname: Zea-Ponce
authors.forename: J D
authors.initials: JD
authors.lastname: Bremner
authors.forename: T M
authors.initials: TM
authors.lastname: Hyde
authors.forename: D S
authors.initials: DS
authors.lastname: Charney
mesh_terms: D000328:Adult; D001923:Brain Chemistry; D005260:Female; D005442:Flumazenil / Q000031:analogs & derivatives*; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D011963:Receptors, GABA-A / Q000032:analysis*; D012016:Reference Values; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D007457:Iodine Radioisotopes; D011963:Receptors, GABA-A; D005442:Flumazenil; C063038:iomazenil