title: Phylogenetic distribution of bicuculline-sensitive gamma-amino-butyric acid (GABA) receptor binding.
abstract: Bicuculline-sensitive [3H]GABA receptor binding was studied in membrane fractions prepared from vertebrate whole brain or invertebrate cephalic ganglia. In tissue not treated with Triton X-100, a significant amount of bicuculline-displaceable [3H]GABA binding was detected in the brains of all vertebrates studied, with the hagfish brain binding over twice as much [3H]GABA as the spiny dogfish, the next oldest species. All other vertebrates bound similar amounts of [3H]GABA, being one-third to one-fourth that observed in the hagfish. In contrast, after Triton treatment, the hagfish displayed the least amount of bicuculline-sensitive [3H]GABA binding and, under those conditions, the amount of binding observed increased in an evolutionary fashion. No measurable bicuculline-sensitive GABA receptor binding was noted in any invertebrate studied. These results suggest that bicuculline-sensitive GABA receptors are present in the brains of all vertebrates and that during the course of evolution there developed a Triton-sensitive substance(s) whose presence modifies the kinetic properties of this receptor site.
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000494:pharmacology*; D001717:Birds; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005399:Fishes; D005724:Ganglia / Q000378:metabolism; D007448:Invertebrates; D007700:Kinetics; D051379:Mice; D010802:Phylogeny; D051381:Rats; D011955:Receptors, Drug / Q000187:drug effects / Q000378:metabolism*; D013045:Species Specificity; D014714:Vertebrates; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D011955:Receptors, Drug; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline