Characterization of two novel N-methyl-D-aspartate antagonists: EAA-090 (2-[8,9-dioxo-2,6-diazabicyclo [5.2.0]non-1(7)-en2-yl]ethylphosphonic acid) and EAB-318 (R-alpha-amino-5-chloro-1-(phosphonomethyl)-1H-benzimidazole-2-propanoic acid hydrochloride).
Two novel N-methyl-d-aspartate (NMDA) antagonists with unique chemical structures, EAA-090 (2-[8,9-dioxo-2, 6-diazabicyclo[5.2.0]non-1(7)-en2-yl]ethylphosphonic acid) and EAB-318 (R-alpha-amino-5-chloro-1-(phosphonomethyl)-1H-benzimidazole-2-propanoic acid hydrochloride), were compared with CGS-19755 (Selfotel) in ligand binding, electrophysiology, and neuroprotection assays. CGS-19755, EAA-090 and EAB-318 inhibited [(3)H]3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid binding to NMDA receptors with IC(50) values of 55, 28, and 7.9 nM, respectively. All three compounds decreased the duration of spontaneous synaptic currents and inhibited NMDA-activated currents in rat hippocampal neurons. IC(50) values for inhibition of current induced by 10 microM NMDA were 795, 477, and 69 nM for CGS-19755, EAA-090, and EAB-318, respectively. The NMDA antagonists protected chick embryo retina slices and cultured rat hippocampal and cortical neurons from glutamate- and NMDA-induced neurotoxicity. In experiments in which different NMDA receptor splice variants and subtypes were expressed in Xenopus oocytes, all three antagonists preferentially blocked NMDA-elicited currents mediated by N-methyl-d-aspartate receptor (NR)1 splice variants containing the N-terminal insertion. They also favored NR2A-versus NR2B- or NR2C-containing NMDA receptors, with EAA-090 showing the greatest selectivity. EAA-090 was 10 times more potent at blocking NR2A-versus NR2B- or NR2C-containing NMDA receptors. In addition to being the most potent NMDA antagonist, EAB-318 inhibited alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors. The combination of NMDA and AMPA/kainate block enabled EAB-318 to protect neurons against ischemia induced cell death.
Sun
Lucy
L
Discovery Neuroscience, Wyeth Research, CN8000, Princeton, NJ 08543, USA.
Chiu
Doreen
D
Kowal
Dianne
D
Simon
Rachelle
R
Smeyne
Michelle
M
Zukin
R Suzanne
RS
Olney
John
J
Baudy
Reinhardt
R
Lin
Stephen
S
D000818:Animals; D053961:Azabicyclo Compounds; D001562:Benzimidazoles / Q000737:chemistry / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry / Q000494:pharmacology*; D002478:Cells, Cultured; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D063065:Organophosphonates; D011422:Propionates / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014982:Xenopus laevis
D053961:Azabicyclo Compounds; D001562:Benzimidazoles; D019086:Bridged Bicyclo Compounds, Heterocyclic; D018691:Excitatory Amino Acid Antagonists; D063065:Organophosphonates; D011422:Propionates; C498147:R-alpha-amino-5-chloro-1-(phosphonomethyl)-1H-benzimidazole-2-propanoic acid hydrochloride; D016194:Receptors, N-Methyl-D-Aspartate; C110623:EAA-090