The in vivo binding kinetics of C-11-iomazenil were compared with those of C-11-flumazenil binding in rhesus monkey brain. The monkey was anesthetized with ketamine and intravenously injected with either C-11-iomazenil or C-11-flumazenil in combination with the coadministration of different doses of non-radioactive flumazenil (0, 5 and 20 mug/kg). The regional distribution of C-11-iomazenil in the brain was similar to that of C-11-flumazenil. but the sensitivity of C-11-iomazenil binding to competitive inhibition by non-radioactive flumazenil was much less than that of C-11-flumazenil binding. A significant reduction in C-11-flumazenil binding in the cerebral cortex was observed with 20 mug/kg of flumazenil, whereas a relatively smaller inhibition of C-11-iomazenil binding in the same region was observed with the same dose of flumazenil. These results suggest that C-11-flumazenil may be a superior radiotracer for estimating benzodiazepine receptor occupancy in the intact brain.
The Reaction of Menthofuran with p-Toluenediazonium Sulfate<sup>1</sup>