Different sensitivities to competitive inhibition of benzodiazepine receptor binding of 11C-iomazenil and 11C-flumazenil in rhesus monkey brain

The in vivo binding kinetics of 11C-iomazenil were compared with those of 11C-flumazenil binding in rhesus monkey brain. The monkey was anesthetized with ketamine and intravenously injected with either 11C-iomazenil or 11C-flumazenil in combination with the coadministration of different doses of non...

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Bibliographic Details
Published in:Annals of nuclear medicine 2001-04, Vol.15 (2), p.137-139
Main Authors: Inoue, O, Hosoi, R, Kobayashi, K, Itoh, T, Gee, A, Suzuki, K
Format: Article
Language:English
Subjects:
Animals
Binding, Competitive
Brain - diagnostic imaging
Brain - metabolism
Carbon Radioisotopes
Flumazenil - analogs & derivatives
Flumazenil - metabolism
Flumazenil - pharmacology
GABA-A Receptor Antagonists
Kinetics
Macaca mulatta
Radioligand Assay
Radiopharmaceuticals
Receptors, GABA-A - metabolism
Tissue Distribution
Tomography, Emission-Computed
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Summary:The in vivo binding kinetics of 11C-iomazenil were compared with those of 11C-flumazenil binding in rhesus monkey brain. The monkey was anesthetized with ketamine and intravenously injected with either 11C-iomazenil or 11C-flumazenil in combination with the coadministration of different doses of non-radioactive flumazenil (0, 5 and 20 microg/kg). The regional distribution of 11C-iomazenil in the brain was similar to that of 11C-flumazenil, but the sensitivity of 11C-iomazenil binding to competitive inhibition by non-radioactive flumazenil was much less than that of 11C-flumazenil binding. A significant reduction in 11C-flumazenil binding in the cerebral cortex was observed with 20 microg/kg of flumazenil, whereas a relatively smaller inhibition of 11C-iomazenil binding in the same region was observed with the same dose of flumazenil. These results suggest that 11C-flumazenil may be a superior radiotracer for estimating benzodiazepine receptor occupancy in the intact brain.
ISSN:0914-7187