Characterization of diazepam-insensitive [3H]Ro 15-4513 binding in rodent brain and cultured cerebellar neuronal cells.
Experiments were performed to characterize diazepam-insensitive [3H]Ro 15-4513 binding sites in discrete regions of rodent brain and cultured rat cerebellar granule cells. Scatchard analysis of [3H]Ro 15-4513 binding in the presence of 10 microM diazepam revealed that diazepam-insensitive binding sites in the rat brain were most abundant in the cerebellum, followed by the hippocampus, cerebral cortex and olfactory bulb. Diazepam-insensitive sites represented approximately 80% of the total [3H]Ro 15-4513 binding sites in the membranes of cultured rat cerebellar granule cells. The Bmax values for total [3H]Ro 15-4513 and [35S]TBPS are almost identical, and 5-6 times larger than that for [3H]diazepam in this preparation. Although some annelated [1,5-a]benzodiazepine analogues such as Ro 15-4513, ro 16-6028, flumazenil and Ro 15-3505, and an imidazothieno-diazepine, Ro 19-4603, showed high affinity for cortical and cerebellar diazepam-insensitive sites, all the annelated benzodiazepine compounds tested showed higher affinity for cerebellar diazepam-insensitive sites than cortical ones. In contrast, a pyrazoloquinoline compound, CGS 8216, and beta-carboline analogues such as beta-carboline-3-carboxylate ethyl ester (beta-CCE) and beta-carboline-3-carboxylate methyl ester (beta-CCM) exhibited higher affinity for cortical than cerebellar sites. These results suggest that diazepam-insensitive sites are heterogeneous in brain areas with respect to ligand specificity.
Ito
Y
Y
Department of Pharmacology, College of Pharmacy, Nihon University, Chiba, Japan.
Abiko
E
E
Mitani
K
K
Fukuda
H
H
D000345:Affinity Labels / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000378:metabolism*; D001569:Benzodiazepines / Q000378:metabolism*; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D003975:Diazepam / Q000494:pharmacology*; D006168:Guinea Pigs; D006624:Hippocampus / Q000378:metabolism; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009474:Neurons / Q000378:metabolism*; D009830:Olfactory Bulb / Q000378:metabolism; D009928:Organ Specificity; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism; D013045:Species Specificity; D014316:Tritium
D000345:Affinity Labels; D001386:Azides; D011963:Receptors, GABA-A; D014316:Tritium; D001569:Benzodiazepines; C042957:Ro 15-4513; D003975:Diazepam