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Quantitative in vivo measurement of central benzodiazepine receptors in the brain of cats by use of positron-emission tomography and [11C]flumazenil

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  • 1 Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, 1-1 Naka-cho, Itabashi-ku, Tokyo 172-0022, Japan.
  • | 2 Department of Veterinary Clinical Pathobiology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 112-0000, Japan.
  • | 3 Present address is the Sakuradai Animal Hospital, 29-6-3 Sakuradai, Aoba-ku, Yokohama 227-0061, Japan.
  • | 4 Department of Ophthalmology and Visual Science, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
  • | 5 Department of Neurosurgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
  • | 6 Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, 1-1 Naka-cho, Itabashi-ku, Tokyo 172-0022, Japan.
  • | 7 Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, 1-1 Naka-cho, Itabashi-ku, Tokyo 172-0022, Japan.
  • | 8 Present address is the National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
  • | 9 Department of Veterinary Clinical Pathobiology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 112-0000, Japan.
  • | 10 Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, 1-1 Naka-cho, Itabashi-ku, Tokyo 172-0022, Japan.
  • | 11 Present address is the Institute of Biomedical Research and Innovation, 2-2 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan.
  • | 12 Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, 1-1 Naka-cho, Itabashi-ku, Tokyo 172-0022, Japan.

Abstract

Objective—To map central benzodiazepine receptors (BZRs) in the brain of cats by use of positron-emission tomography (PET) and [11C]flumazenil.

Animals—6 male cats that weighed between 2.0 and 3.6 kg.

Procedure—Brain images obtained by PET evaluation of [11C]flumazenil were superimposed on T2-weighted magnetic-resonance imaging (MRI) scans of the same cats. Detailed anatomic regions, such as the cerebral cortex, striatum, thalamus, midbrain, and cerebellum, on the PET images were evident by PETMRI registration. Regional binding of [11C]flumazenil to BZRs was quantitatively measured by use of a model with 2 tissue compartments and 4 variables.

Results—The highest value for distribution volume was observed in the cerebral cortex, and the lowest value was found in the midbrain of cats.

Conclusions and Clinical Relevance—Binding of [11C]flumazenil to BZRs in the brain of cats can be quantitatively measured by use of PET with the aid of PET-MRI registration. It is difficult to diagnose changes in these neuroreceptors within the field of current veterinary science. In the future, PET should prove useful for investigating and diagnosing brain disorders in animals in clinical settings. (Am J Vet Res 2003;64:999–1002)

Abstract

Objective—To map central benzodiazepine receptors (BZRs) in the brain of cats by use of positron-emission tomography (PET) and [11C]flumazenil.

Animals—6 male cats that weighed between 2.0 and 3.6 kg.

Procedure—Brain images obtained by PET evaluation of [11C]flumazenil were superimposed on T2-weighted magnetic-resonance imaging (MRI) scans of the same cats. Detailed anatomic regions, such as the cerebral cortex, striatum, thalamus, midbrain, and cerebellum, on the PET images were evident by PETMRI registration. Regional binding of [11C]flumazenil to BZRs was quantitatively measured by use of a model with 2 tissue compartments and 4 variables.

Results—The highest value for distribution volume was observed in the cerebral cortex, and the lowest value was found in the midbrain of cats.

Conclusions and Clinical Relevance—Binding of [11C]flumazenil to BZRs in the brain of cats can be quantitatively measured by use of PET with the aid of PET-MRI registration. It is difficult to diagnose changes in these neuroreceptors within the field of current veterinary science. In the future, PET should prove useful for investigating and diagnosing brain disorders in animals in clinical settings. (Am J Vet Res 2003;64:999–1002)