The effect of CGX-1007 and CI-1041, novel NMDA receptor antagonists, on NMDA receptor-mediated EPSCs.
The N-methyl-D-aspartate (NMDA) receptor-gated ion channel is comprised of at least one NR1 subunit and any of four NR2 subunits (NR2A-D). The NR2 subunit confers different pharmacological and kinetic properties to the receptor. CGX-1007 (Conantokin G), a 17-amino acid polypeptide isolated from the venom of Conus geographus, is a novel NMDA receptor antagonist that is thought to be selective for the NR2B subunit. CGX-1007 has been reported to have highly potent, broad-spectrum anticonvulsant activity in animal seizure models. CI-1041 is an investigational compound, which also possesses anticonvulsant activity and has been shown to be highly selective for NR2B containing NMDA receptors. Although both CI-1041 and CGX-1007 are reportedly NR2B specific antagonists, they differ in their ability to block amygdala-kindled seizures, suggesting that the mechanism of action of these compounds differs. The present study was designed to test the hypothesis that CI-1041 and CGX-1007 would differentially modulate the function of NMDA receptors at excitatory synapses. Using the whole cell patch clamp technique, CGX-1007 and CI-1041 were found to block CA1 pyramidal cell, NMDA receptor-mediated excitatory postsynaptic currents (N-EPSCs) in a concentration-dependent manner in hippocampal slices from P4-P6 animals. In contrast, only CGX-1007 decreased NMDA receptor-mediated EPSC peak amplitude in slices from adult animals. The CGX-1007 block of peak amplitude was accompanied by a similar concentration-dependent decrease in decay kinetics of NMDA receptor-mediated EPSCs. These results suggest that while CI-1041 may be selective for NMDA receptors containing the NR2B subunit, CGX-1007 appears to be less selective than previously reported.
Barton
Matthew E
ME
Anticonvulsant Drug Development Program, Department of Pharmacology and Toxicology, University of Utah, 20 S 2030 E, RM 408, Salt Lake City, UT 84112, USA.
White
H Steve
HS
Wilcox
Karen S
KS
D000818:Animals; D001583:Benzoxazoles / Q000494:pharmacology*; D020916:Conotoxins / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects* / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D010880:Piperidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000502:physiology
D001583:Benzoxazoles; D020916:Conotoxins; D018691:Excitatory Amino Acid Antagonists; D010880:Piperidines; D016194:Receptors, N-Methyl-D-Aspartate; C481484:besonprodil; C055407:conotoxin GV