[125I]thienylphencyclidine, a novel ligand for the NMDA receptor.
We have monitored the binding of [125I]thienylphencyclidine ([125I]TCP), a novel high affinity radioiodinated ligand that specifically recognizes the NMDA (N-methyl-D-aspartate) receptor in rat brain membranes. [125I]TCP binds with an affinity of about 30 nM, and recognizes a similar number of binding sites to previously employed ligands for this receptor. [125I]TCP binding is characterized by slow association and dissociation rates, and the latter can be modified by the addition of Mg2+ or Zn2+, as previously described for [3H]dizocilpine ([3H]MK801). Other phencyclidine-like ligands displaced [125I]TCP binding with the order of potency dizocilpine greater than thienylphencyclidine greater than ITCP greater than phencyclidine greater than ketamine. The binding of [125I]TCP was also increased by NMDA and glycine-site agonists and inhibited by antagonists of these sites. Surprisingly, however, the polyamines spermidine and spermine did not increase [125I]TCP, even though the polyamine antagonist arcaine was an effective inhibitor of binding. These results show that [125I]TCP is a useful ligand for the NMDA receptor complex that binds to the receptor in a manner that is qualitatively distinct from previously described ligands.
Reynolds
I J
IJ
Department of Pharmacology, University of Pittsburgh, PA 15261.
Rothermund
K
K
Rajdev
S
S
Fauq
A H
AH
Kozikowski
A P
AP
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D005998:Glycine / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007700:Kinetics; D010622:Phencyclidine / Q000031:analogs & derivatives / Q000378:metabolism*; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*
D005971:Glutamates; D007457:Iodine Radioisotopes; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D010622:Phencyclidine; D005998:Glycine