A subclass of GABAA/benzodiazepine receptor exclusively localized in the limbic system.
An in vivo saturation study using 11C-labelled Ro15-4513 with high specific radioactivity (> 70 GBq mumol-1) revealed the presence of very high-affinity and high-affinity binding sites (Kd values in the amygdala approximately 0.4 and 18.7 nM, respectively) in the gamma-aminobutyric acid type A/benzodiazepine (GABAA/BZ) receptor in the living monkey brain. Subtraction of an image obtained using [11C]Ro15-4513 with low specific radioactivity from an image obtained by that with high specific radioactivity, both of which were scanned with a high spatial resolution positron emission tomography camera, demonstrated that the very high-affinity sites are exclusively localized in the limbic system, such as in the amygdala, hippocampus, anterior cingulate, septum, nucleus accumbens and insular cortex. The localization of the very high-affinity binding sites, which may be derived from a subclass of central GABAA/BZ receptors, might account for the anxiolytic effect of BZ analogues.
Onoe
H
H
Subfemtomole Biorecognition Project, Research Development Corporation of Japan, Osaka, Japan.
Tsukada
H
H
Nishiyama
S
S
Nakanishi
S
S
Inoue
O
O
Långström
B
B
Watanabe
Y
Y
D000345:Affinity Labels; D000818:Animals; D001345:Autoradiography; D001386:Azides; D001569:Benzodiazepines; D002250:Carbon Radioisotopes; D005260:Female; D005442:Flumazenil; D018757:GABA Modulators; D007091:Image Processing, Computer-Assisted; D007553:Isotope Labeling; D008032:Limbic System / Q000033:anatomy & histology / Q000378:metabolism*; D008253:Macaca mulatta; D011963:Receptors, GABA-A / Q000378:metabolism*; D014055:Tomography, Emission-Computed
D000345:Affinity Labels; D001386:Azides; D002250:Carbon Radioisotopes; D018757:GABA Modulators; D011963:Receptors, GABA-A; D001569:Benzodiazepines; D005442:Flumazenil; C042957:Ro 15-4513