Novel fluorine-18 PET radiotracers based on flumazenil for GABAA imaging in the brain.
Nucl Med Biol
; 40(7): 901-5, 2013 Oct.
Article
en En
| MEDLINE
| ID: mdl-23890694
ABSTRACT
INTRODUCTION:
Two 7-fluoroimidazobenzodiazepines (AH114726 and GEH120348), analogs of flumazenil, were labeled with fluorine-18 and evaluated as alternative radioligands for in vivo imaging of the GABAA/benzodiazepine receptor by comparing them to [(11)C]flumazenil in rhesus monkey.METHODS:
Radiotracers were prepared from the corresponding nitro-precursors in an automated synthesis module, and primate imaging studies were conducted on a Concorde MicroPET P4 scanner. The brain was imaged for 60 (12 × 5 min frames) or 90 min (18 × 5 min frames), and data was reconstructed using the 3D MAP algorithm. Specificity of [(18)F]AH114726 and [(18)F]GEH120348 was confirmed by displacement studies using unlabeled flumazenil.RESULTS:
[(18)F]GEH120348 and [(18)F]AH114726 were obtained in 13-24% yields (end of synthesis) with high chemical (>95%) and radiochemical (>99%) purities, and high specific activities (2061 ± 985 Ci/mmol). The in vivo pharmacokinetics of [(18)F]AH114726 and [(18)F]GEH120348 were determined in a non-human primate and directly compared with [(11)C]flumazenil. Both fluorine-18 radioligands showed time-dependent regional brain distributions that correlated with the distribution of [(11)C]flumazenil and the known concentrations of GABAA/benzodiazepine receptors in the monkey brain. [(18)F]AH114726 exhibited maximal brain uptake and tissue time-radioactivity curves that were most similar to [(11)C]flumazenil. In contrast, [(18)F]GEH120348 showed higher initial brain uptake but very different pharmacokinetics with continued accumulation of radioactivity into the cortical regions of high GABA/benzodiazepine receptor concentrations and very little clearance from the regions of low receptor densities. Rapid washout of both radiotracers occurred upon treatment with unlabeled flumazenil.CONCLUSION:
The ease of the radiochemical synthesis, together with in vivo brain pharmacokinetics most similar to [(11)C]flumazenil, support that [(18)F]AH114726 is a suitable option for imaging the GABAA receptor.Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Encéfalo
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Radioisótopos de Flúor
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Flumazenil
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Receptores de GABA-A
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Tomografía de Emisión de Positrones
Límite:
Animals
Idioma:
En
Revista:
Nucl Med Biol
Asunto de la revista:
BIOLOGIA
/
MEDICINA NUCLEAR
Año:
2013
Tipo del documento:
Article
País de afiliación:
Estados Unidos