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

Ann Nucl Med. 2001 Apr;15(2):137-9. doi: 10.1007/BF02988604.

Abstract

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.

Publication types

  • Comparative Study

MeSH terms

  • 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

Substances

  • Carbon Radioisotopes
  • GABA-A Receptor Antagonists
  • Radiopharmaceuticals
  • Receptors, GABA-A
  • Flumazenil
  • iomazenil