[3H]CGP 39653: a new N-methyl-D-aspartate antagonist radioligand with low nanomolar affinity in rat brain.
CGP 39653 (D,L-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acid) was initially discovered to inhibit the binding of [3H]L-glutamate and [3H]3-[+/-)2-carboxypiperazin-4-yl)-propyl-1- phosphonic acid [( 3H]CPP) with Ki values of 230 and 5 nM, respectively. The radiolabeled compound [3H]CGP 39653 binds to rat frontal cortical membranes in a saturable and reversible manner. Analysis of saturation experiments revealed that the ligand labels one binding site with a Kd value of 6 nM. Competition experiments indicated that the order of potency of a number of competitive excitatory amino acid agonist and antagonist compounds was similar to that found previously for other N-methyl-D-aspartate (NMDA) receptor ligands. In contrast to these competitive inhibitors, which produced steep inhibition curves, glycine inhibited binding in a complex manner. When the functional activity of the unlabeled compound was explored, CGP 39653 blocked NMDA-evoked depolarizations in the rat cortical wedge in vitro and inhibited L-glutamate stimulated [3H]N(1-[2-thienyl]cyclohexyl)3,4-piperidine [( 3H]TCP) binding in cortical membranes. These results suggest that [3H]CGP 39653 selectively binds to the NMDA receptor as an antagonist with high affinity and is currently the ligand of choice for labeling the NMDA receptor.
Sills
M A
MA
Ciba-Geigy Corporation, Research Department, Summit, NJ 07901.
Fagg
G
G
Pozza
M
M
Angst
C
C
Brundish
D E
DE
Hurt
S D
SD
Wilusz
E J
EJ
Williams
M
M
D015763:2-Amino-5-phosphonovalerate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010622:Phencyclidine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*
D005971:Glutamates; D016194:Receptors, N-Methyl-D-Aspartate; C069052:CGP 39653; D018698:Glutamic Acid; D015763:2-Amino-5-phosphonovalerate; C012058:tenocyclidine; D010622:Phencyclidine