Binding characteristics of a potent AMPA receptor antagonist [3H]Ro 48-8587 in rat brain.
A new AMPA receptor antagonist, Ro 48-8587, was characterized pharmacologically in vitro. It is highly potent and selective for AMPA receptors as shown by its effects on [3H]AMPA, [3H] kainate, and [3H] MK-801 binding to rat brain membranes and on AMPA- or NMDA-induced depolarization in rat cortical wedges. [3H]Ro 48-8587 bound with a high affinity (KD = 3 nM) to a single population of binding sites with a Bmax of 1 pmol/mg of protein in rat whole brain membranes. [3H]Ro 48-8587 binding to rat whole brain membranes was inhibited by several compounds with the following rank order of potency: Ro 48-8587 > 6-nitro-7-sulphamoylbenzo[f] quinoxaline-2,3-dione (NBQX) > YM 90K > 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) > quisqualate > AMPA > glutamate > kainate > NMDA. The distribution and abundance of specific binding sites (approximately 95% of total) in sections of rat CNS, revealed by quantitative receptor radioautography and image analysis, indicated a very discrete localization. Highest binding values were observed in cortical layers (binding in layers 1 and 2 > binding in layers 3-6), hippocampal formation, striatum, dorsal septum, reticular thalamic nucleus, cerebellar molecular layer, and spinal cord dorsal horn. At 1 nM, the values for specific binding were highest in the cortical layers 1 and 2 and lowest in the brainstem (approximately 2.6 and 0.4 pmol/mg of protein, respectively). Ro 48-8587 is a potent and selective AMPA receptor antagonist with improved binding characteristics (higher affinity, selectivity, and specific binding) compared with those previously reported.
Mutel
V
V
Pharma Division, Preclinical CNS Research, F. Hoffmann-La Roche Ltd., Basel, Switzerland.
Trube
G
G
Klingelschmidt
A
A
Messer
J
J
Bleuel
Z
Z
Humbel
U
U
Clifford
M M
MM
Ellis
G J
GJ
Richards
J G
JG
D000818:Animals; D014151:Anti-Anxiety Agents; D001569:Benzodiazepines / Q000494:pharmacology; D001923:Brain Chemistry; D016291:Dizocilpine Maleate / Q000378:metabolism / Q000494:pharmacology; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000378:metabolism / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000378:metabolism / Q000494:pharmacology*; D007093:Imidazoles / Q000378:metabolism / Q000494:pharmacology*; D017403:In Situ Hybridization; D007608:Kainic Acid / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D016202:N-Methylaspartate / Q000378:metabolism / Q000494:pharmacology; D011799:Quinazolines / Q000378:metabolism / Q000494:pharmacology*; D011810:Quinoxalines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D018091:Receptors, AMPA / Q000819:agonists / Q000037:antagonists & inhibitors* / Q000235:genetics*; D014316:Tritium; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000378:metabolism / Q000494:pharmacology
D014151:Anti-Anxiety Agents; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D007093:Imidazoles; D011799:Quinazolines; D011810:Quinoxalines; D012333:RNA, Messenger; D018091:Receptors, AMPA; C112933:Ro 48-8587; D014316:Tritium; C061950:GYKI 52466; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D001569:Benzodiazepines; C086162:6-(1H-imidazol-1-yl)-7-nitro-2,3(1H,4H)-quinoxalinedione; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D007608:Kainic Acid