Antagonism of flurazepam and other effects of Ro15-1788, PK8165 and Ro5-4864 on the GABA-A receptor complex in rat cuneate nucleus.
In slices of rat cuneate nucleus, responses to the GABA-A receptor agonist muscimol were potentiated by flurazepam. The maximal potentiation by 1 microM flurazepam was antagonized by the neuronal benzodiazepine receptor ligand Ro15-1788 3 microM, by the quinoline derivative PK8165 0.1 microM and by the peripheral-type benzodiazepine receptor ligand Ro5-4864 0.1 microM. Another ligand for the peripheral-type benzodiazepine receptor, PK11195 10 microM, enhanced the potentiating effect of a submaximal concentration of flurazepam 0.1 microM and prevented the antagonism of flurazepam by Ro5-4864. At much higher concentrations of these drugs, additional effects were seen. Ro15-1788 30 microM and PK11195 30 microM each caused small potentiations of muscimol while Ro5-4864 30 microM caused a small antagonism. Ro15-1788 30 microM, PK8165 100 microM and Ro5-4864 30 microM all antagonized the potentiation of muscimol by pentobarbitone 10 microM; also, PK8165 and Ro5-4864 enhanced the potency of picrotoxin as an antagonist of muscimol. It is concluded that both Ro5-4864 and PK8165 have several distinct effects on the GABA-A receptor complex, all of which could result in reduced responses to muscimol.
D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D001570:Benzodiazepinones / Q000494:pharmacology; D004357:Drug Synergism; D005442:Flumazenil; D005479:Flurazepam / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D009118:Muscimol; D010424:Pentobarbital / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects*
D000927:Anticonvulsants; D001570:Benzodiazepinones; D005442:Flumazenil; D005479:Flurazepam; D009118:Muscimol; D010424:Pentobarbital; D010852:Picrotoxin; D011804:Quinolines; D011963:Receptors, GABA-A; C028513:4'-chlorodiazepam; C030078:pipequaline