title: Anion-dependent modulation of [3H]muscimol binding and of GABA-stimulated [3H]flunitrazepam binding by picrotoxin and related CNS convulsants.
abstract: Picrotoxin, isopropylbicyclophosphate (IPTBO) and related CNS-convulsants have allosteric effects on the binding of ligands to the GABA/benzodiazepine receptor complex. When binding experiments were performed at 23 degrees C and at 35 degrees C, these drugs inhibited [3H]muscimol binding and muscimol- or GABA-stimulated [3H]flunitrazepam binding, respectively. Both effects required the presence of C1-, Br-, I- but not of F- or SO4(2-). Picrotoxin and IPTBO could only partially inhibit [3H]muscimol binding. In contrast other GABA antagonists and convulsants like bicuculline, 3 alpha-hydroxy-16-imino-5 beta-17-aza-androstan-11-one (R 5135), strychnine and d-tubocurarine interferred completely with [3H]muscimol binding, also in the absence of those ions mentioned above which were essential for the effects of picrotoxin. Our results support the notion that drugs like picrotoxin and IPTBO which interfere with the GABA receptor effector system, may lead to an allosteric perturbation of GABA-recognition sites.
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism; D014151:Anti-Anxiety Agents / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D003292:Convulsants / Q000494:pharmacology*; D005445:Flunitrazepam / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009118:Muscimol / Q000378:metabolism*; D010080:Oxazoles / Q000378:metabolism*; D010852:Picrotoxin / Q000494:pharmacology*; D051381:Rats; D011955:Receptors, Drug / Q000378:metabolism; D011963:Receptors, GABA-A; D013331:Strychnine / Q000494:pharmacology; D014403:Tubocurarine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D000838:Anions; D014151:Anti-Anxiety Agents; D003292:Convulsants; D005445:Flunitrazepam; D009118:Muscimol; D010080:Oxazoles; D010852:Picrotoxin; D011955:Receptors, Drug; D011963:Receptors, GABA-A; D013331:Strychnine; D014403:Tubocurarine; D005680:gamma-Aminobutyric Acid