title: Phylogenetic conservation of the benzodiazepine binding sites: pharmacological evidence.
abstract: Phylogenetic research can help to elucidate the structure of the GABA/benzodiazepine receptor complex. In this study the evolution of the beta-carboline binding site was traced to see whether it paralleled that of the benzodiazepine binding site. The ratio of [3H]ethyl-beta-carboline-3-carboxylate (beta-CCE) to [3H]flunitrazepam (FNZ) binding sites was determined in several nonmammalian species. The results further substantiate the tight link between these two binding sites. Photoaffinity labelling of the benzodiazepine receptor (BZR) has revealed phylogenetic variation of the molecular weight of the benzodiazepine binding proteins. The IC50 values for inhibition of [3H]FNZ by various compounds which are active at the central benzodiazepine receptors were determined in three phylogenetically distant species that each showed distinct subunit patterns. In these species, the respective affinities of the compounds were remarkably similar, suggesting that the binding sites for benzodiazepines are conserved in higher bony fishes and tetrapods. The conserved binding sites, in addition to recent immunological results obtained in other research groups, provide further evidence for the existence of the GABA/BZR as an isoreceptor complex.
authors.affiliation: Institut Für Humangenetik, Universität Bonn, F.R.G.
authors.forename: W
authors.initials: W
authors.lastname: Friedl
authors.forename: J
authors.initials: J
authors.lastname: Hebebrand
authors.forename: S
authors.initials: S
authors.lastname: Rabe
authors.forename: P
authors.initials: P
authors.lastname: Propping
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001001:Anura; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D002243:Carbolines / Q000378:metabolism; D004372:Ducks; D005399:Fishes; D005445:Flunitrazepam / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D010777:Photochemistry; D010802:Phylogeny; D011869:Radioligand Assay; D051381:Rats; D011963:Receptors, GABA-A / Q000378:metabolism*; D013045:Species Specificity; D013552:Swine
chemical_list: D000345:Affinity Labels; D002243:Carbolines; D011963:Receptors, GABA-A; D005445:Flunitrazepam; C024915:beta-carboline-3-carboxylic acid ethyl ester