title: Distinction of benzodiazepine agonists from antagonists by photoaffinity labelling of benzodiazepine receptors in vitro.
abstract: When membranes of rat cerebellum are exposed to UV light in the presence of flunitrazepam this ligand can be incorporated into one of the assumed 4 benzodiazepine binding sites of the GABA-benzodiazepine receptor complex. This irreversible incorporation of flunitrazepam, in contrast to reversible binding of this substance, leads to conformational changes of the remaining 3 benzodiazepine binding sites which result in a decreased affinity of benzodiazepine agonists, but not of benzodiazepine antagonists. The investigation of the affinity of drugs for [3H]benzodiazepine antagonist binding before and after photoaffinity labelling of benzodiazepine receptors with flunitrazepam can therefore be used as a sensitive and simple test to distinguish between agonists and antagonists in vitro.
mesh_terms: D000818:Animals; D014151:Anti-Anxiety Agents / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001667:Binding, Competitive; D002243:Carbolines / Q000378:metabolism; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism*; D005445:Flunitrazepam / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D011955:Receptors, Drug / Q000187:drug effects / Q000378:metabolism*; D011963:Receptors, GABA-A; D014466:Ultraviolet Rays
chemical_list: D014151:Anti-Anxiety Agents; D002243:Carbolines; D011956:Receptors, Cell Surface; D011955:Receptors, Drug; D011963:Receptors, GABA-A; C026072:1-methyl-beta-carboline-3-carboxylic acid; D005445:Flunitrazepam