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Landau AM, Jakobsen S, Thomsen MB, Alstrup AKO, Orlowski D, Jacobsen J, Wegener G, Mørk A, Sørensen JCH, Doudet DJ. Combined In Vivo Microdialysis and PET Studies to Validate [ 11C]Yohimbine Binding as a Marker of Noradrenaline Release. Biomolecules 2023; 13:674. [PMID: 37189421 PMCID: PMC10136072 DOI: 10.3390/biom13040674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Revised: 04/05/2023] [Accepted: 04/07/2023] [Indexed: 05/17/2023] Open
Abstract
The noradrenaline system attracts attention for its role in mood disorders and neurodegenerative diseases but the lack of well-validated methods impairs our understanding when assessing its function and release in vivo. This study combines simultaneous positron emission tomography (PET) and microdialysis to explore if [11C]yohimbine, a selective antagonist radioligand of the α2 adrenoceptors, may be used to assess in vivo changes in synaptic noradrenaline during acute pharmacological challenges. Anesthetised Göttingen minipigs were positioned in a head holder in a PET/CT device. Microdialysis probes were placed in the thalamus, striatum and cortex and dialysis samples were collected every 10 min. Three 90 min [11C]yohimbine scans were acquired: at baseline and at two timepoints after the administration of amphetamine (1-10 mg/kg), a non-specific releaser of dopamine and noradrenaline, or nisoxetine (1 mg/kg), a specific noradrenaline transporter inhibitor. [11C]yohimbine volumes of distribution (VT) were obtained using the Logan kinetic model. Both challenges induced a significant decrease in yohimbine VT, with time courses reflecting their different mechanisms of action. Dialysis samples revealed a significant increase in noradrenaline extracellular concentrations after challenge and an inverse correlation with changes in yohimbine VT. These data suggest that [11C]yohimbine can be used to evaluate acute variations in synaptic noradrenaline concentrations after pharmacological challenges.
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Affiliation(s)
- Anne Marlene Landau
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, A701, Palle Juul Jensens Boulevard 99, 8200 Aarhus, Denmark
- Department of Nuclear Medicine & PET-Center, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Steen Jakobsen
- Department of Nuclear Medicine & PET-Center, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Majken Borup Thomsen
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, A701, Palle Juul Jensens Boulevard 99, 8200 Aarhus, Denmark
- Department of Nuclear Medicine & PET-Center, Aarhus University Hospital, 8200 Aarhus, Denmark
| | | | - Dariusz Orlowski
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Jan Jacobsen
- Department of Nuclear Medicine & PET-Center, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Gregers Wegener
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, A701, Palle Juul Jensens Boulevard 99, 8200 Aarhus, Denmark
| | - Arne Mørk
- Synaptic Transmission, H. Lundbeck A/S, Ottiliavej 9, Valby, 2500 Copenhagen, Denmark
| | | | - Doris J. Doudet
- Department of Medicine/Neurology, University of British Columbia, 2221 Wesbrook Mall, Vancouver, BC V6T 2B5, Canada;
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Radioligand binding analysis of α 2 adrenoceptors with [ 11C]yohimbine in brain in vivo: Extended Inhibition Plot correction for plasma protein binding. Sci Rep 2017; 7:15979. [PMID: 29167492 PMCID: PMC5700124 DOI: 10.1038/s41598-017-16020-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 10/23/2017] [Indexed: 11/23/2022] Open
Abstract
We describe a novel method of kinetic analysis of radioligand binding to neuroreceptors in brain in vivo, here applied to noradrenaline receptors in rat brain. The method uses positron emission tomography (PET) of [11C]yohimbine binding in brain to quantify the density and affinity of α2 adrenoceptors under condition of changing radioligand binding to plasma proteins. We obtained dynamic PET recordings from brain of Spraque Dawley rats at baseline, followed by pharmacological challenge with unlabeled yohimbine (0.3 mg/kg). The challenge with unlabeled ligand failed to diminish radioligand accumulation in brain tissue, due to the blocking of radioligand binding to plasma proteins that elevated the free fractions of the radioligand in plasma. We devised a method that graphically resolved the masking of unlabeled ligand binding by the increase of radioligand free fractions in plasma. The Extended Inhibition Plot introduced here yielded an estimate of the volume of distribution of non-displaceable ligand in brain tissue that increased with the increase of the free fraction of the radioligand in plasma. The resulting binding potentials of the radioligand declined by 50–60% in the presence of unlabeled ligand. The kinetic unmasking of inhibited binding reflected in the increase of the reference volume of distribution yielded estimates of receptor saturation consistent with the binding of unlabeled ligand.
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Landau AM, Dyve S, Jakobsen S, Alstrup AK, Gjedde A, Doudet DJ. Acute Vagal Nerve Stimulation Lowers α2 Adrenoceptor Availability: Possible Mechanism of Therapeutic Action. Brain Stimul 2015; 8:702-7. [DOI: 10.1016/j.brs.2015.02.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 01/23/2015] [Accepted: 02/07/2015] [Indexed: 12/13/2022] Open
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Nahimi A, Jakobsen S, Munk OL, Vang K, Phan JA, Rodell A, Gjedde A. Mapping α2 adrenoceptors of the human brain with 11C-yohimbine. J Nucl Med 2015; 56:392-8. [PMID: 25635132 DOI: 10.2967/jnumed.114.145565] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED A previous study from this laboratory suggested that (11)C-yohimbine, a selective α2-adrenoceptor antagonist, is an appropriate ligand for PET of α2 adrenoceptors that passes readily from blood to brain tissue in pigs but not in rodents. To test usefulness in humans, we determined blood-brain clearances, volumes of distribution, and receptor availability by means of PET with (11)C-yohimbine in healthy male adults. METHODS We recorded the distribution of (11)C-yohimbine with 90-min dynamic PET and sampled arterial blood to measure intact (11)C-yohimbine in plasma. For analysis, we coregistered PET images to individual MR images and automatically identified 27 volumes of interest. We used 1-tissue-compartment graphical analysis with 6 linearized solutions of the fundamental binding equation, with the metabolite-corrected arterial plasma curves as input function, to estimate the kinetic parameters of (11)C-yohimbine. With the lowest steady-state distribution volume (VT), determined in the corpus callosum, we calculated the binding potential (receptor availability) of the radioligand in other regions. RESULTS The linear regressions yielded similar estimates of the kinetic parameters. The cortical values of VT ranged from 0.82 mL cm(-3) in the right frontal cortex to 0.46 mL cm(-3) in the corpus callosum, with intermediate VT values in subcortical structures. Binding potentials averaged 0.6-0.8 in the cortex and 0.2-0.5 in subcortical regions. CONCLUSION The maps of (11)C-yohimbine binding to α2 adrenoceptors in human brain had the highest values in cortical areas and hippocampus, with moderate values in subcortical structures, as found also in vitro. The results confirm the usefulness of the tracer (11)C-yohimbine for mapping α2 adrenoceptors in human brain in vivo.
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Affiliation(s)
- Adjmal Nahimi
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Aarhus, Denmark
| | - Steen Jakobsen
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Aarhus, Denmark
| | - Ole L Munk
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Aarhus, Denmark
| | - Kim Vang
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Aarhus, Denmark
| | - Jenny A Phan
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Aarhus, Denmark
| | - Anders Rodell
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Aarhus, Denmark
| | - Albert Gjedde
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Aarhus, Denmark Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland; and Department of Neurology, McGill University, Montreal, Quebec, Canada
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Finnema SJ, Hughes ZA, Haaparanta-Solin M, Stepanov V, Nakao R, Varnäs K, Varrone A, Arponen E, Marjamäki P, Pohjanoksa K, Vuorilehto L, Babalola PA, Solin O, Grimwood S, Sallinen J, Farde L, Scheinin M, Halldin C. Amphetamine decreases α2C-adrenoceptor binding of [11C]ORM-13070: a PET study in the primate brain. Int J Neuropsychopharmacol 2015; 18:pyu081. [PMID: 25522417 PMCID: PMC4360244 DOI: 10.1093/ijnp/pyu081] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The neurotransmitter norepinephrine has been implicated in psychiatric and neurodegenerative disorders. Examination of synaptic norepinephrine concentrations in the living brain may be possible with positron emission tomography (PET), but has been hampered by the lack of suitable radioligands. METHODS We explored the use of the novel α2C-adrenoceptor antagonist PET tracer [(11)C]ORM-13070 for measurement of amphetamine-induced changes in synaptic norepinephrine. The effect of amphetamine on [(11)C]ORM-13070 binding was evaluated ex vivo in rat brain sections and in vivo with PET imaging in monkeys. RESULTS Microdialysis experiments confirmed amphetamine-induced elevations in rat striatal norepinephrine and dopamine concentrations. Regional [(11)C]ORM-13070 receptor binding was high in the striatum and low in the cerebellum. After injection of [(11)C]ORM-13070 in rats, mean striatal specific binding ratios, determined using cerebellum as a reference region, were 1.4±0.3 after vehicle pretreatment and 1.2±0.2 after amphetamine administration (0.3mg/kg, subcutaneous). Injection of [(11)C]ORM-13070 in non-human primates resulted in mean striatal binding potential (BP ND) estimates of 0.65±0.12 at baseline. Intravenous administration of amphetamine (0.5 and 1.0mg/kg, i.v.) reduced BP ND values by 31-50%. Amphetamine (0.3mg/kg, subcutaneous) increased extracellular norepinephrine (by 400%) and dopamine (by 270%) in rat striata. CONCLUSIONS Together, these results indicate that [(11)C]ORM-13070 may be a useful tool for evaluation of synaptic norepinephrine concentrations in vivo. Future studies are required to further understand a potential contribution of dopamine to the amphetamine-induced effect.
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Affiliation(s)
- Sjoerd J Finnema
- Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Finnema, Stepanov, Nakao, Varnäs, Varrone, Farde, and Halldin); Pfizer, Neuroscience Research Unit, Cambridge, MA (Drs Hughes, Babalola, and Grimwood); University of Turku, Turku PET Centre, Turku, Finland (Drs Haaparanta-Solin, Arponen, Marjamäki, and Solin); University of Turku, Department of Pharmacology, Drug Development and Therapeutics, and Turku University Hospital, Unit of Clinical Pharmacology, Turku, Finland (Drs Pohjanoksa, Vuorilehto, and Scheinin); Orion Corporation, Orion Pharma, Research and Development, Turku, Finland (Dr Sallinen); AstraZeneca, Translational Science Center at Karolinska Institutet, Stockholm, Sweden (Dr Farde)
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Lehto J, Hirvonen MM, Johansson J, Kemppainen J, Luoto P, Naukkarinen T, Oikonen V, Arponen E, Rouru J, Sallinen J, Scheinin H, Vuorilehto L, Finnema SJ, Halldin C, Rinne JO, Scheinin M. Validation of [(11) C]ORM-13070 as a PET tracer for alpha2c -adrenoceptors in the human brain. Synapse 2015; 69:172-81. [PMID: 25530024 DOI: 10.1002/syn.21798] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 12/03/2014] [Accepted: 12/10/2014] [Indexed: 12/24/2022]
Abstract
This study explored the use of the α2C -adrenoceptor PET tracer [(11) C]ORM-13070 to monitor α2C -AR occupancy in the human brain. The subtype-nonselective α2 -AR antagonist atipamezole was administered to eight healthy volunteer subjects to determine its efficacy and potency (Emax and EC50 ) at inhibiting tracer uptake. We also explored whether the tracer could reveal changes in the synaptic concentrations of endogenous noradrenaline in the brain, in response to several pharmacological and sensory challenge conditions. We assessed occupancy from the bound-to-free ratio measured during 5-30 min post injection. Based on extrapolation of one-site binding, the maximal extent of inhibition of striatal [(11) C]ORM-13070 uptake (Emax ) achievable by atipamezole was 78% (95% CI 69-87%) in the caudate nucleus and 65% (53-77%) in the putamen. The EC50 estimates of atipamezole (1.6 and 2.5 ng/ml, respectively) were in agreement with the drug's affinity to α2C -ARs. These findings represent clear support for the use of [(11) C]ORM-13070 for monitoring drug occupancy of α2C -ARs in the living human brain. Three of the employed noradrenaline challenges were associated with small, approximately 10-16% average reductions in tracer uptake in the dorsal striatum (atomoxetine, ketamine, and the cold pressor test; P < 0.05 for all), but insulin-induced hypoglycemia did not affect tracer uptake. The tracer is suitable for studying central nervous system receptor occupancy by α2C -AR ligands in human subjects. [(11) C]ORM-13070 also holds potential as a tool for in vivo monitoring of synaptic concentrations of noradrenaline, but this remains to be further evaluated in future studies.
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Affiliation(s)
- Jussi Lehto
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Turku, Finland; Clinical Research Services Turku CRST, Turku, Finland; Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland
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Arponen E, Helin S, Marjamäki P, Grönroos T, Holm P, Löyttyniemi E, Någren K, Scheinin M, Haaparanta-Solin M, Sallinen J, Solin O. A PET Tracer for Brain α2C Adrenoceptors, (11)C-ORM-13070: Radiosynthesis and Preclinical Evaluation in Rats and Knockout Mice. J Nucl Med 2014; 55:1171-7. [PMID: 24799619 DOI: 10.2967/jnumed.113.135574] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 03/17/2014] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED We report the development of a PET tracer for α2C adrenoceptor imaging and its preliminary preclinical evaluation. α2C adrenoceptors in the human brain may be involved in various neuropsychiatric disorders, such as depression, schizophrenia, and neurodegenerative diseases. PET tracers are needed for imaging of this receptor system in vivo. METHODS High-specific-activity (11)C-ORM-13070 (1-[(S)-1-(2,3-dihydrobenzo[1,4]dioxin-2-yl)methyl]-4-(3-(11)C-methoxymethylpyridin-2-yl)-piperazine) was synthesized by (11)C-methylation of O-desmethyl-ORM-13070 with (11)C-methyl triflate, which was prepared from cyclotron-produced (11)C-methane via (11)C-methyl iodide. Rats and mice were investigated in vivo with PET and ex vivo with autoradiography. The specificity of (11)C-ORM-13070 binding to α2 adrenoceptors was demonstrated in rats pretreated with atipamezole, an α2 adrenoceptor antagonist. The α2C adrenoceptor selectivity of the tracer was determined by comparing tracer binding in wild-type and α2A- and α2AC adrenoceptor knockout (KO) mice. (11)C-ORM-13070 and its radioactive metabolites in rat plasma and brain tissue were analyzed with radio-high-performance liquid chromatography and mass spectroscopy. Human radiation dose estimates were extrapolated from rat biodistribution data. RESULTS The radiochemical yield, calculated from initial cyclotron-produced (11)C-methane, was 9.6% ± 2.7% (decay-corrected to end of bombardment). The specific activity of the product was 640 ± 390 GBq/μmol (decay-corrected to end of synthesis). The radiochemical purity exceeded 99% in all syntheses. The highest levels of tracer binding were observed in the striatum and olfactory tubercle of rats and control and α2A KO mice-that is, in the brain regions known to contain the highest densities of α2C adrenoceptors. In rats pretreated with atipamezole and in α2AC KO mice, (11)C tracer binding in the striatum and olfactory tubercle was low, similar to that of the frontal cortex and thalamus, regions with low densities of α2C adrenoceptors. Two radioactive metabolites were found in rat plasma, but only one of them was found in the brain; their identity was not revealed. The estimated effective radiation dose was comparable with the average exposure level in PET studies with (11)C tracers. CONCLUSION An efficient method for the radiosynthesis of (11)C-ORM-13070 was developed. (11)C-ORM-13070 emerged as a potential novel radiotracer for in vivo imaging of brain α2C adrenoceptors.
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Affiliation(s)
- Eveliina Arponen
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Semi Helin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Päivi Marjamäki
- MediCity/PET Preclinical Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Tove Grönroos
- MediCity/PET Preclinical Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Patrik Holm
- Orion Pharma, Research and Development, Turku, Finland
| | | | - Kjell Någren
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Mika Scheinin
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, and Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland; and
| | - Merja Haaparanta-Solin
- MediCity/PET Preclinical Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | | | - Olof Solin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland Accelerator Laboratory, Åbo Akademi University, Turku, Finland
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Krystal AD, Richelson E, Roth T. Review of the histamine system and the clinical effects of H1 antagonists: Basis for a new model for understanding the effects of insomnia medications. Sleep Med Rev 2013; 17:263-72. [DOI: 10.1016/j.smrv.2012.08.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 08/09/2012] [Accepted: 08/09/2012] [Indexed: 11/27/2022]
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Landau AM, Doudet DJ, Jakobsen S. Amphetamine challenge decreases yohimbine binding to α2 adrenoceptors in Landrace pig brain. Psychopharmacology (Berl) 2012; 222:155-63. [PMID: 22227612 DOI: 10.1007/s00213-011-2632-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 12/21/2011] [Indexed: 11/29/2022]
Abstract
RATIONALE The noradrenaline (NA) system is implicated in neurodegenerative and psychiatric disorders; however, our understanding is impaired by the lack of well-validated radioligands to assess NA function and release. Yohimbine, an α2 adrenoceptor antagonist, has recently been developed as a carbon-11 [11C]-labeled radioligand for positron emission tomography (PET) imaging studies. OBJECTIVES Here we explore the hypothesis that yohimbine can be used as an in vivo tracer of NA receptor binding and release during amphetamine challenges in Landrace pigs. METHODS Pigs underwent baseline PET scans with [11C]yohimbine and were then challenged with 10 mg/kg d-amphetamine 20 min prior to a second [11C]yohimbine scan. Using the Logan analysis model, volumes of distribution were calculated from fits of the kinetic data 25-90 min post-yohimbine injection. RESULTS Amphetamine decreased [11C]yohimbine volume of distribution in the brain regions under investigation, including the thalamus, caudate nucleus, and cortical regions. CONCLUSION These data suggest that the binding of [11C]yohimbine to α2 adrenoceptors may be displaceable by increases in synaptic concentrations of the endogenous ligand, NA, and possibly dopamine, suggesting the possibility that [11C]yohimbine may be used as a surrogate marker of NA release in vivo.
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Affiliation(s)
- Anne M Landau
- Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Norrebrogade 44, Building 10G, Aarhus C 8000, Denmark
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Virdee K, Cumming P, Caprioli D, Jupp B, Rominger A, Aigbirhio FI, Fryer TD, Riss PJ, Dalley JW. Applications of positron emission tomography in animal models of neurological and neuropsychiatric disorders. Neurosci Biobehav Rev 2012; 36:1188-216. [PMID: 22342372 DOI: 10.1016/j.neubiorev.2012.01.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 01/26/2012] [Accepted: 01/31/2012] [Indexed: 01/08/2023]
Abstract
Positron emission tomography (PET) provides dynamic images of the biodistribution of radioactive tracers in the brain. Through application of the principles of compartmental analysis, tracer uptake can be quantified in terms of specific physiological processes such as cerebral blood flow, cerebral metabolic rate, and the availability of receptors in brain. Whereas early PET studies in animal models of brain diseases were hampered by the limited spatial resolution of PET instruments, dedicated small-animal instruments now provide molecular images of rodent brain with resolution approaching 1mm, the theoretic limit of the method. Major applications of PET for brain research have consisted of studies of animal models of neurological disorders, notably Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD), stroke, epilepsy and traumatic brain injury; these studies have particularly benefited from selective neurochemical lesion models (PD), and also transgenic rodent models (AD, HD). Due to their complex and uncertain pathophysiologies, corresponding models of neuropsychiatric disorders have proven more difficult to establish. Historically, there has been an emphasis on PET studies of dopamine transmission, as assessed with a range of tracers targeting dopamine synthesis, plasma membrane transporters, and receptor binding sites. However, notable recent breakthroughs in molecular imaging include the development of greatly improved tracers for subtypes of serotonin, cannabinoid, and metabotropic glutamate receptors, as well as noradrenaline transporters, amyloid-β and neuroinflammatory changes. This article reviews the considerable recent progress in preclinical PET and discusses applications relevant to a number of neurological and neuropsychiatric disorders in humans.
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Affiliation(s)
- Kanwar Virdee
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, CB2 3EB, UK
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PET kinetics of radiolabeled antidepressant, [N-methyl-11C]mirtazapine, in the human brain. EJNMMI Res 2011; 1:36. [PMID: 22214419 PMCID: PMC3261093 DOI: 10.1186/2191-219x-1-36] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 12/15/2011] [Indexed: 11/10/2022] Open
Abstract
Background We compared six kinetic models with and without the requirement of arterial cannulation for estimating the binding potential of [N-methyl-11C]mirtazapine in the living human brain. Methods Distribution volumes of [N-methyl-11C]mirtazapine in brain regions were estimated using single- and two-tissue compartment models as well as a graphical plasma input model. The two-tissue compartment model provided a direct estimate of the binding potentials of [N-methyl-11C]mirtazapine in brain regions, while binding potentials of the single-tissue compartment model and the graphical plasma input model were estimated indirectly from ratios of distribution volumes in brain regions. We obtained also direct estimates of binding potentials using a graphical reference tissue model and two nonlinear reference tissue models. Results The two-tissue compartment model required several fits with different initial guesses for avoiding negative values of parameters. Despite the extra fits, estimates of distribution volumes and binding potentials of [N-methyl-11C]mirtazapine obtained by the two-tissue compartment model were far more variable than those produced by the other methods. The graphical plasma input method and the graphical reference tissue method provided estimates of the binding potential that correlated closely, but differed in magnitude. The single-tissue compartment model provided relatively low estimates of binding potentials with curves that failed to fit the data as well as the three other methods that used the entire series of positron emission tomography data. The reference tissue method and the simplified reference tissue method provided similar, consistent estimates of binding potentials. However, certain assumptions of the simplified reference tissue method may not be fulfilled by the radioligand. Conclusion The reference tissue method is appropriate for estimating the binding potential of [N-methyl-11C]mirtazapine in regions of the human brain so that the binding potential of [N-methyl-11C]mirtazapine can be estimated without arterial cannulation.
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Cumming P, Borghammer P. Molecular imaging and the neuropathologies of Parkinson's disease. Curr Top Behav Neurosci 2011; 11:117-48. [PMID: 22034053 DOI: 10.1007/7854_2011_165] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The main motor symptoms of Parkinson's disease (PD) are linked to degeneration of the nigrostriatal dopamine (DA) fibers, especially those innervating the putamen. This degeneration can be assessed in molecular imaging studies with presynaptic tracers such as [(18)F]-fluoro-L-DOPA (FDOPA) and ligands for DA transporter ligands. However, the pathologies of PD are by no means limited to nigrostriatal loss. Results of post mortem and molecular imaging studies reveal parallel degenerations of cortical noradrenaline (NA) and serotonin (5-HT) innervations, which may contribute to affective and cognitive changes of PD. Especially in advanced PD, cognitive impairment can come to resemble that seen in Alzheimer's dementia, as can the degeneration of acetylcholine innervations arising in the basal forebrain. The density of striatal DA D(2) receptors increases in early untreated PD, consistent with denervation upregulation, but there is an accelerated rate of DA receptor loss as the disease advances. Animal studies and post mortem investigations reveal changes in brain opioid peptide systems, but these are poorly documented in imaging studies of PD. Relatively minor changes in the binding sites for GABA are reported in cortex and striatum of PD patients. There remains some controversy about the expression of the 18 kDa translocator protein (TSPO) in activated microglia as an indicator of an active inflammatory component of neurodegeneration in PD. A wide variety of autonomic disturbances contribute to the clinical syndrome of PD; the degeneration of myocardial sympathetic innervation can be revealed in SPECT studies of PD patients with autonomic failure. Considerable emphasis has been placed on investigations of cerebral blood flow and energy metabolism in PD. Due to the high variance of these physiological estimates, researchers have often employed normalization procedures for the sensitive detection of perturbations in relatively small patient groups. However, a widely used normalization to the global mean must be used with caution, as it can result in spurious findings of relative hypermetabolic changes in subcortical structures. A meta-analysis of the quantitative studies to date shows that there is in fact widespread hypometabolism and cerebral blood flow in the cerebral cortex, especially in frontal cortex and parietal association areas. These changes can bias the use of global mean normalization, and probably represent the pathophysiological basis of the cognitive impairment of PD.
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Affiliation(s)
- Paul Cumming
- Department of Nuclear Medicine, Ludwig-Maximilian's University of Munich, Munich, Germany,
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Kawamura K, Akiyama M, Yui J, Yamasaki T, Hatori A, Kumata K, Wakizaka H, Takei M, Nengaki N, Yanamoto K, Fukumura T, Zhang MR. In vivo evaluation of limiting brain penetration of probes for α(2C)-adrenoceptor using small-animal positron emission tomography. ACS Chem Neurosci 2010; 1:520-8. [PMID: 22778842 DOI: 10.1021/cn1000364] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 05/25/2010] [Indexed: 11/30/2022] Open
Abstract
To evaluate in vivo brain penetration of α(2C)-adrenoceptor (α(2C)-AR) antagonists as a therapeutic agent, we synthesized two new (11)C-labeled selective α(2C)-AR antagonists 4-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-2-aryl-7-methoxybenzofuran ([(11)C]MBF) and acridin-9-yl-[4-(4-methylpiperazin-1-yl)phenyl]amine ([(11)C]JP-1302) as α(2C)-AR-selective positron emission tomography (PET) probes. The radiochemical yield, specific activity, and radiochemical purity of these probes was appropriate for injection. To evaluate whether the brain penetration of these probes is related to the function of two major drug efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), we performed PET studies using wild-type and P-gp/Bcrp knockout mice. In wild-type mice, the radioactivity level after injection with [(11)C]MBF initially increased and effluxed immediately from the brain, whereas that with [(11)C]JP-1302 was distributed throughout the brain. However, the regional distribution of radioactivity after injection with [(11)C]JP-1302 in the brain was different from that of α(2C)-ARs. In P-gp/Bcrp knockout mice, uptake of [(11)C]MBF was approximately 3.7-fold higher and that of [(11)C]JP-1302 was approximately 1.6-fold higher than those in wild-type mice. These results indicate that brain penetration of the two PET probes was affected by modulation of P-gp and Bcrp functions.
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Affiliation(s)
| | | | - Joji Yui
- Department of Molecular Probes and
| | | | | | | | - Hidekatsu Wakizaka
- Department of Molecular Probes and
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555, Japan
| | - Makoto Takei
- Department of Molecular Probes and
- Tokyo Nuclear Services Co., Ltd., Tokyo 110-0005, Japan
| | - Nobuki Nengaki
- Department of Molecular Probes and
- SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Kazuhiko Yanamoto
- Department of Molecular Probes and
- Division of Health Sciences, Graduate School of Medicine, Osaka University, Suita 565-0871, Japan
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Prabhakaran J, Majo VJ, Milak MS, Mali P, Savenkova L, Mann JJ, Parsey RV, Kumar JD. Synthesis and in vivo evaluation of [11C]MPTQ: A potential PET tracer for alpha2A-adrenergic receptors. Bioorg Med Chem Lett 2010; 20:3654-7. [DOI: 10.1016/j.bmcl.2010.04.099] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 04/20/2010] [Accepted: 04/21/2010] [Indexed: 12/28/2022]
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Smith DF, Stork BS, Wegener G, Ashkanian M, Jakobsen S, Bender D, Audrain H, Vase KH, Hansen SB, Videbech P, Rosenberg R. [11C]Mirtazapine binding in depressed antidepressant nonresponders studied by PET neuroimaging. Psychopharmacology (Berl) 2009; 206:133-40. [PMID: 19536526 DOI: 10.1007/s00213-009-1587-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Accepted: 06/01/2009] [Indexed: 11/27/2022]
Abstract
RATIONALE Lack of benefit from antidepressant drug therapy is a major source of human suffering, affecting at least 25% of people with major depressive disorder. We want to know whether nonresponse to antidepressants can be linked to aberrant neuroreceptor binding. OBJECTIVE This study aims to assess the antidepressant binding in brain regions of depressed nonresponders compared with healthy controls. MATERIALS AND METHODS Healthy volunteers and depressed subjects who had failed to benefit from at least 2 antidepressant treatments were recruited by newspaper advertisements. All subjects had received no antidepressant medication for at least 2 months before positron emission tomography (PET) that was carried out with [11C]mirtazapine. Kinetic parameters of [11C]mirtazapine were determined from PET data in selected brain regions by the simplified reference tissue model. RESULTS Binding potentials of [11C]mirtazapine in cerebral cortical regions were lower in depressed nonresponders than in healthy controls. Removal rates of [11C]mirtazapine were higher in diencephalic regions of depressed nonresponders than in healthy controls. CONCLUSIONS PET neuroimaging with [11C]mirtazapine showed aberrant neuroreceptor binding in brain regions of depressed subjects who had failed to benefit from treatment with antidepressant drugs.
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Affiliation(s)
- Donald F Smith
- Center for Psychiatric Research, Psychiatric Hospital of Aarhus University, Risskov, 8240, Denmark.
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Smith DF, Hansen SB, Jakobsen S, Bender D, Audrain H, Ashkanian M, Stork BS, Minuzzi L, Hall H, Rosenberg R. Neuroimaging of mirtazapine enantiomers in humans. Psychopharmacology (Berl) 2008; 200:273-9. [PMID: 18566802 DOI: 10.1007/s00213-008-1208-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 05/12/2008] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Mirtazapine is a racemic antidepressant with a multireceptor profile. Previous studies have shown that the enantiomers of mirtazapine have different pharmacologic effects in the brain of laboratory animals. MATERIALS AND METHODS In the present study, we used positron emission tomography (PET) and autoradiography to study effects of (R)- and (S)-[(11)C]mirtazapine in the human brain. Detailed brain imaging by PET using three methods of kinetic data analysis showed no reliable differences between regional binding potentials of (R)- and (S)-[(11)C]mirtazapine in healthy subjects. RESULTS Autoradiographic studies carried out in whole hemispheres of human brain tissue showed, however, that (R)- and (S)-mirtazapine differ markedly as inhibitors of [(3)H]clonidine binding at alpha(2)-adrenoceptors. CONCLUSION The multireceptor binding profiles of mirtazapine enantiomers, along with individual differences between subjects, may preclude PET neuroimaging from demonstrating reliable differences between the regional distribution and binding of (R)- and (S)-[(11)C]mirtazapine in the living human brain.
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Affiliation(s)
- Donald F Smith
- Center for Psychiatric Research, Psychiatric Hospital of Aarhus University, 8240, Risskov, Denmark.
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Smith DF, Stork BS, Wegener G, Jakobsen S, Bender D, Audrain H, Jensen SB, Hansen SB, Rodell A, Rosenberg R. Receptor occupancy of mirtazapine determined by PET in healthy volunteers. Psychopharmacology (Berl) 2007; 195:131-8. [PMID: 17653532 DOI: 10.1007/s00213-007-0877-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 06/22/2007] [Indexed: 10/23/2022]
Abstract
RATIONALE Molecular tools are needed for assessing anti-depressant actions by positron emission tomography (PET) in the living human brain. OBJECTIVES This study determined whether [(11)C]mirtazapine is an appropriate molecular tool for use with PET to estimate the magnitude of neuroreceptor occupancy produced by daily intake of mirtazapine. METHODS This study used a randomised, double-blind, placebo-controlled, parallel-group, within-subject design. Eighteen healthy volunteers were PET-scanned twice with [(11)C]mirtazapine; once under baseline condition and again after receiving either placebo or mirtazapine (7.5 or 15 mg) for 5 days. We determined kinetic parameters of [(11)C]mirtazapine in brain regions by the simplified reference region method and used binding potential values to calculate receptor occupancy produced by mirtazapine. RESULTS Serum concentrations of mirtazapine ranged from 33 to 56 nmol/l after five daily doses of 7.5 mg mirtazapine and were between 41 and 74 nmol/l after 15 mg mirtazapine. Placebo treatment failed to alter the binding potential of [(11)C]mirtazapine from baseline values, whereas daily intake of mirtazapine markedly decreased the binding potential in cortex, amygdala and hippocampus. Receptor occupancy ranged from 74 to 96% in high-binding regions of the brain after five daily doses of 7.5 mg or 15 mg mirtazapine, whereas 17-48% occupancy occurred in low-binding regions. CONCLUSIONS [(11)C]Mirtazapine together with PET can determine the degree of receptor occupancy produced by daily doses of mirtazapine in regions of the living human brain.
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Affiliation(s)
- Donald F Smith
- Center for Psychiatric Research, Psychiatric Hospital of Aarhus University, 8240, Risskov, Denmark.
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Lind NM, Moustgaard A, Jelsing J, Vajta G, Cumming P, Hansen AK. The use of pigs in neuroscience: Modeling brain disorders. Neurosci Biobehav Rev 2007; 31:728-51. [PMID: 17445892 DOI: 10.1016/j.neubiorev.2007.02.003] [Citation(s) in RCA: 365] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 02/05/2007] [Accepted: 02/18/2007] [Indexed: 11/22/2022]
Abstract
The use of pigs in neuroscience research has increased in the past decade, which has seen broader recognition of the potential of pigs as an animal for experimental modeling of human brain disorders. The volume of available background data concerning pig brain anatomy and neurochemistry has increased considerably in recent years. The pig brain, which is gyrencephalic, resembles the human brain more in anatomy, growth and development than do the brains of commonly used small laboratory animals. The size of the pig brain permits the identification of cortical and subcortical structures by imaging techniques. Furthermore, the pig is an increasingly popular laboratory animal for transgenic manipulations of neural genes. The present paper focuses on evaluating the potential for modeling symptoms, phenomena or constructs of human brain diseases in pigs, the neuropsychiatric disorders in particular. Important practical and ethical aspects of the use of pigs as an experimental animal as pertaining to relevant in vivo experimental brain techniques are reviewed. Finally, current knowledge of aspects of behavioral processes including learning and memory are reviewed so as to complete the summary of the status of pigs as a species suitable for experimental models of diverse human brain disorders.
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Affiliation(s)
- Nanna Marie Lind
- Department of Experimental Medicine, University of Copenhagen, Panum Institute, Blegdamsvej 3B, Copenhagen N, Denmark.
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