In vitro binding of [(11)C]raclopride with ultrahigh specific activity in rat brain determined by homogenate assay and autoradiography.

OBJECTIVE The aim of this study was to characterize the in vitro binding of [(11)C]raclopride with ultrahigh specific activity (SA) in the striatum and cerebral cortex of rat brain. METHODS [(11)C]Raclopride, a dopamine D(2) receptor ligand, with an ultrahigh SA of 4880+/-2360 GBq/micromol (132+/-64 Ci/micromol, n=25) was synthesized. In vitro binding experiment was performed using brain homogenate assay and autoradiography (ARG). RESULTS In vitro homogenate assay demonstrated that high SA [(11)C]raclopride (2520-6340 GBq/micromol; 68-171 Ci/micromol) had two-affinity (high and low) binding sites in the striatum and cerebral cortex of rat brain. In the striatum, K(d,high) and B(max,high) values were 0.005+/-0.002 nM and 0.19+/-0.04 fmol/mg tissue, respectively, while K(d,low) and B(max,low) values were 2.2+/-1.0 nM and 35.8+/-16.4 fmol/mg tissue, respectively. In the cerebral cortex, K(d,high) and B(max,high) values were 0.061+/-0.087 nM and 0.2+/-0.2 fmol/mg tissue, respectively, while K(d,low) and B(max,low) values were 2.5+/-3.2 nM and 5.5+/-4.8 fmol/mg tissue, respectively. On the other hand, only one binding site was found in the striatum and no binding site was identified in the cerebral cortex using low SA [(11)C]raclopride (44 GBq/micromol; 1.2 Ci/micromol). In vitro ARG for the rat brain using high SA [(11)C]raclopride (6212 GBq/micromol; 168 Ci/micromol) gave a coronal image of the striatum and cerebral cortex with a higher signal/noise ratio than using low SA [(11)C]raclopride (40 GBq/micromol; 1.1 Ci/micromol). CONCLUSION Using ultrahigh SA [(11)C]raclopride for the in vitro homogenate assay, we succeeded in detecting two-affinity binding sites of [(11)C]raclopride, not only in the striatum but also in the cerebral cortex of rat brain.

[1]  Paul Cumming,et al.  Parametric mapping of binding in human brain of D2 receptor ligands of different affinities. , 2005, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[2]  Marie-Claude Asselin,et al.  Quantification of PET Studies with the Very High-Affinity Dopamine D2/D3 Receptor Ligand [11C]FLB 457: Re-Evaluation of the Validity of using a Cerebellar Reference Region , 2007, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[3]  P. Molinoff,et al.  Quantitative autoradiographic localization of the D1 and D2 subtypes of dopamine receptors in rat brain , 1986, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[4]  M. Senda,et al.  Quantitative ex vivo and in vitro receptor autoradiography using 11C-labeled ligands and an imaging plate: a study with a dopamine D2-like receptor ligand [11C]nemonapride. , 1999, Nuclear medicine and biology.

[5]  Christer Halldin,et al.  A PET-study of [11C]FLB 457 binding to extrastriatal D2-dopamine receptors in healthy subjects and antipsychotic drug-treated patients , 1997, Psychopharmacology.

[6]  Bernard Bendriem,et al.  Quantitation of Extrastriatal D2 Receptors Using a Very High-Affinity Ligand (FLB 457) and the Multi-Injection Approach , 1999, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[7]  K Suzuki,et al.  Reproducibility of [11C]FLB 457 binding in extrastriatal regions , 2001, Nuclear medicine communications.

[8]  G. Sedvall,et al.  PET STUDIES OF DOPAMINE RECEPTORS IN RELATION TO ANTIPSYCHOTIC DRUG TREATMENT , 1992, Clinical neuropharmacology.

[9]  Hans-Georg Buchholz,et al.  The Striatal and Extrastriatal D2/D3 Receptor-Binding Profile of Clozapine in Patients with Schizophrenia , 2006, Neuropsychopharmacology.

[10]  Christer Halldin,et al.  Extrastriatal dopamine D2 receptor density and affinity in the human brain measured by 3D PET. , 1999, International Journal of Neuropsychopharmacology.

[11]  Mohammad Sib Ansari,et al.  Amphetamine-Induced Displacement of [18F] Fallypride in Striatum and Extrastriatal Regions in Humans , 2006, Neuropsychopharmacology.

[12]  B. Scatton,et al.  Autoradiographic localization and quantification of dopamine D2 receptors in normal human brain with [3H]N-n-propylnorapomorphine , 1986, Brain Research.

[13]  G. Gessa,et al.  [3H] (-)sulpiride binding in rat striatum, cortex and anterior pituitary: an improved assay. , 1987, Pharmacological research communications.

[14]  Mitul A Mehta,et al.  Is psychological stress in man associated with increased striatal dopamine levels?: A [11C]raclopride PET study , 2006, Synapse.

[15]  K. Suzuki,et al.  Specific activity of [11C]CO2 generated in a N2 gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy , 2000 .

[16]  P S Goldman-Rakic,et al.  Dopamine D2 receptors in the cerebral cortex: distribution and pharmacological characterization with [3H]raclopride. , 1989, Proceedings of the National Academy of Sciences of the United States of America.

[17]  P. Goldman-Rakic,et al.  Differential regulation of D2 and D4 dopamine receptor mRNAs in the primate cerebral cortex vs. neostriatum: effects of chronic treatment with typical and atypical antipsychotic drugs. , 1997, The Journal of pharmacology and experimental therapeutics.

[18]  Hiroshi Ito,et al.  Effects of repetitive transcranial magnetic stimulation on [11C]raclopride binding and cognitive function in patients with depression. , 2006, Journal of affective disorders.

[19]  P S Goldman-Rakic,et al.  Quantitative autoradiography of major neurotransmitter receptors in the monkey striate and extrastriate cortex , 1988, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[20]  S O Ogren,et al.  Specific in vitro and in vivo binding of 3H-raclopride. A potent substituted benzamide drug with high affinity for dopamine D-2 receptors in the rat brain. , 1985, Biochemical pharmacology.

[21]  Christer Halldin,et al.  Central D2-dopamine receptor occupancy in relation to antipsychotic drug effects: A double-blind PET study of schizophrenic patients , 1993, Biological Psychiatry.

[22]  C. Halldin,et al.  Quantification of [11C]FLB 457 Binding to Extrastriatal Dopamine Receptors in the Human Brain , 1999, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[23]  D. Jewett,et al.  A simple synthesis of [11C]methyl triflate. , 1992, International journal of radiation applications and instrumentation. Part A, Applied radiation and isotopes.

[24]  Mark Slifstein,et al.  Effect of amphetamine on [18F]fallypride in vivo binding to D2 receptors in striatal and extrastriatal regions of the primate brain: Single bolus and bolus plus constant infusion studies , 2004, Synapse.

[25]  Christer Halldin,et al.  Differentiation of extrastriatal dopamine D2 receptor density and affinity in the human brain using PET , 2004, NeuroImage.

[26]  J Noguchi,et al.  Automated synthesis of the ultra high specific activity of [11C]Ro15-4513 and its application in an extremely low concentration region to an ARG study. , 2003, Nuclear medicine and biology.

[27]  S. Stone-Elander,et al.  Stereoselective binding of 11C-raclopride in living human brain — a search for extrastriatal central D2-dopamine receptors by PET , 2004, Psychopharmacology.

[28]  Kazuhiko Yanai,et al.  Evaluation of the binding characteristics of [5-(11)C-methoxy]Donepezil in the rat brain for in vivo visualization of acetylcholinesterase. , 2003, Journal of pharmacological sciences.

[29]  L. Potter,et al.  D-2 dopamine receptors in the frontal cortex of rat and human. , 1985, Life sciences.

[30]  N. Volkow,et al.  Comparison of two PET radioligands for imaging extrastriatal dopamine receptorsin the human brain , 1993, Synapse.

[31]  A. Dagher,et al.  Conditioned Dopamine Release in Humans: A Positron Emission Tomography [11C]Raclopride Study with Amphetamine , 2007, The Journal of Neuroscience.

[32]  G. Sedvall,et al.  Quantitative analysis of D2 dopamine receptor binding in the living human brain by PET. , 1986, Science.

[33]  U Ruotsalainen,et al.  PET study on striatal dopamine D2 receptor changes during the progression of early parkinson's disease , 1993, Movement disorders : official journal of the Movement Disorder Society.