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D'Elia A, Schiavi S, Soluri A, Massari R, Soluri A, Trezza V. Role of Nuclear Imaging to Understand the Neural Substrates of Brain Disorders in Laboratory Animals: Current Status and Future Prospects. Front Behav Neurosci 2020; 14:596509. [PMID: 33362486 PMCID: PMC7759612 DOI: 10.3389/fnbeh.2020.596509] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 11/23/2020] [Indexed: 12/18/2022] Open
Abstract
Molecular imaging, which allows the real-time visualization, characterization and measurement of biological processes, is becoming increasingly used in neuroscience research. Scintigraphy techniques such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) provide qualitative and quantitative measurement of brain activity in both physiological and pathological states. Laboratory animals, and rodents in particular, are essential in neuroscience research, providing plenty of models of brain disorders. The development of innovative high-resolution small animal imaging systems together with their radiotracers pave the way to the study of brain functioning and neurotransmitter release during behavioral tasks in rodents. The assessment of local changes in the release of neurotransmitters associated with the performance of a given behavioral task is a turning point for the development of new potential drugs for psychiatric and neurological disorders. This review addresses the role of SPECT and PET small animal imaging systems for a better understanding of brain functioning in health and disease states. Brain imaging in rodent models faces a series of challenges since it acts within the boundaries of current imaging in terms of sensitivity and spatial resolution. Several topics are discussed, including technical considerations regarding the strengths and weaknesses of both technologies. Moreover, the application of some of the radioligands developed for small animal nuclear imaging studies is discussed. Then, we examine the changes in metabolic and neurotransmitter activity in various brain areas during task-induced neural activation with special regard to the imaging of opioid, dopaminergic and cannabinoid receptors. Finally, we discuss the current status providing future perspectives on the most innovative imaging techniques in small laboratory animals. The challenges and solutions discussed here might be useful to better understand brain functioning allowing the translation of preclinical results into clinical applications.
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Affiliation(s)
- Annunziata D'Elia
- Institute of Biochemistry and Cell Biology, National Research Council of Italy (CNR), Rome, Italy.,Section of Biomedical Sciences and Technologies, Department of Science, University "Roma Tre", Rome, Italy
| | - Sara Schiavi
- Section of Biomedical Sciences and Technologies, Department of Science, University "Roma Tre", Rome, Italy
| | - Andrea Soluri
- Institute of Biochemistry and Cell Biology, National Research Council of Italy (CNR), Rome, Italy
| | - Roberto Massari
- Institute of Biochemistry and Cell Biology, National Research Council of Italy (CNR), Rome, Italy
| | - Alessandro Soluri
- Institute of Biochemistry and Cell Biology, National Research Council of Italy (CNR), Rome, Italy
| | - Viviana Trezza
- Section of Biomedical Sciences and Technologies, Department of Science, University "Roma Tre", Rome, Italy
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Szöllősi D, Hegedűs N, Veres DS, Futó I, Horváth I, Kovács N, Martinecz B, Dénes Á, Seifert D, Bergmann R, Lebeda O, Varga Z, Kaleta Z, Szigeti K, Máthé D. Evaluation of Brain Nuclear Medicine Imaging Tracers in a Murine Model of Sepsis-Associated Encephalopathy. Mol Imaging Biol 2019; 20:952-962. [PMID: 29736562 PMCID: PMC6244542 DOI: 10.1007/s11307-018-1201-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Purpose The purpose of this study was to evaluate a set of widely used nuclear medicine imaging agents as possible methods to study the early effects of systemic inflammation on the living brain in a mouse model of sepsis-associated encephalopathy (SAE). The lipopolysaccharide (LPS)-induced murine systemic inflammation model was selected as a model of SAE. Procedures C57BL/6 mice were used. A multimodal imaging protocol was carried out on each animal 4 h following the intravenous administration of LPS using the following tracers: [99mTc][2,2-dimethyl-3-[(3E)-3-oxidoiminobutan-2-yl]azanidylpropyl]-[(3E)-3-hydroxyiminobutan-2-yl]azanide ([99mTc]HMPAO) and ethyl-7-[125I]iodo-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylate ([125I]iomazenil) to measure brain perfusion and neuronal damage, respectively; 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) to measure cerebral glucose uptake. We assessed microglia activity on another group of mice using 2-[6-chloro-2-(4-[125I]iodophenyl)-imidazo[1,2-a]pyridin-3-yl]-N-ethyl-N-methyl-acetamide ([125I]CLINME). Radiotracer uptakes were measured in different brain regions and correlated. Microglia activity was also assessed using immunohistochemistry. Brain glutathione levels were measured to investigate oxidative stress. Results Significantly reduced perfusion values and significantly enhanced [18F]FDG and [125I]CLINME uptake was measured in the LPS-treated group. Following perfusion compensation, enhanced [125I]iomazenil uptake was measured in the LPS-treated group’s hippocampus and cerebellum. In this group, both [18F]FDG and [125I]iomazenil uptake showed highly negative correlation to perfusion measured with ([99mTc]HMPAO uptake in all brain regions. No significant differences were detected in brain glutathione levels between the groups. The CD45 and P2Y12 double-labeling immunohistochemistry showed widespread microglia activation in the LPS-treated group. Conclusions Our results suggest that [125I]CLINME and [99mTc]HMPAO SPECT can be used to detect microglia activation and brain hypoperfusion, respectively, in the early phase (4 h post injection) of systemic inflammation. We suspect that the enhancement of [18F]FDG and [125I]iomazenil uptake in the LPS-treated group does not necessarily reflect neural hypermetabolism and the lack of neuronal damage. They are most likely caused by processes emerging during neuroinflammation, e.g., microglia activation and/or immune cell infiltration. Electronic supplementary material The online version of this article (10.1007/s11307-018-1201-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dávid Szöllősi
- Department of Biophysics and Radiation Biology, Semmelweis Univ, Budapest, H-1094, Hungary
| | - Nikolett Hegedűs
- Department of Biophysics and Radiation Biology, Semmelweis Univ, Budapest, H-1094, Hungary
| | - Dániel S Veres
- Department of Biophysics and Radiation Biology, Semmelweis Univ, Budapest, H-1094, Hungary
| | - Ildikó Futó
- Department of Biophysics and Radiation Biology, Semmelweis Univ, Budapest, H-1094, Hungary
| | - Ildikó Horváth
- Department of Biophysics and Radiation Biology, Semmelweis Univ, Budapest, H-1094, Hungary
| | - Noémi Kovács
- CROmed Translational Research Centers, Budapest, H-1047, Hungary
| | - Bernadett Martinecz
- Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Ádám Dénes
- Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Daniel Seifert
- Nuclear Physics Institute of the CAS, CZ 250 68, Rez, Czech Republic
| | - Ralf Bergmann
- Helmholz-Zentrum Dresden-Rossendorf, Radiopharmazie Radiopharmaceutische Biologie, Dresden, Germany
| | - Ondřej Lebeda
- Nuclear Physics Institute of the CAS, CZ 250 68, Rez, Czech Republic
| | - Zoltán Varga
- Department of Biophysics and Radiation Biology, Semmelweis Univ, Budapest, H-1094, Hungary.,Biological Nanochemistry Research Group, Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zoltán Kaleta
- Progressio Fine Chemical Engineering Ltd, Székesfehérvár, Hungary
| | - Krisztián Szigeti
- Department of Biophysics and Radiation Biology, Semmelweis Univ, Budapest, H-1094, Hungary.
| | - Domokos Máthé
- CROmed Translational Research Centers, Budapest, H-1047, Hungary
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