TY - JOUR
T1 - Binding characterization of N-(2-chloro-5-thiomethylphenyl)-N′-(3-[ 3 H] 3 methoxy phenyl)-N′-methylguanidine ([ 3 H]GMOM), a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist
AU - Metaxas, Athanasios
AU - van Berckel, Bart N. M.
AU - Klein, Pieter J.
AU - Verbeek, Joost
AU - Nash, Emily C.
AU - Kooijman, Esther J. M.
AU - Renjaän, V. ronique A.
AU - Golla, Sandeep S. V.
AU - Boellaard, Ronald
AU - Christiaans, Johannes A. M.
AU - Windhorst, Albert D.
AU - Leysen, Josée E.
PY - 2019/2/1
Y1 - 2019/2/1
N2 - Labeled with carbon-11, N-(2-chloro-5-thiomethylphenyl)-N′-(3-methoxyphenyl)-N′-methylguanidine ([ 11 C]GMOM) is currently the only positron emission tomography (PET) tracer that has shown selectivity for the ion-channel site of N-methyl-D-aspartate (NMDA) receptors in human imaging studies. The present study reports on the selectivity profile and in vitro binding properties of GMOM. The compound was screened on a panel of 80 targets, and labeled with tritium ([ 3 H]GMOM). The binding properties of [ 3 H]GMOM were compared to those of the reference ion-channel ligand [ 3 H](+)-dizocilpine maleate ([ 3 H]MK-801), in a set of concentration-response, homologous and heterologous inhibition, and association kinetics assays, performed with repeatedly washed rat forebrain preparations. GMOM was at least 70-fold more selective for NMDA receptors compared to all other targets examined. In homologous inhibition and concentration-response assays, the binding of [ 3 H]GMOM was regulated by NMDA receptor agonists, albeit in a less prominent manner compared to [ 3 H]MK-801. Scatchard transformation of homologous inhibition data produced concave upward curves for [ 3 H]GMOM and [ 3 H]MK-801. The radioligands showed bi-exponential association kinetics in the presence of 100 μmol L −1 l-glutamate/30 μmol L −1 glycine. [ 3 H]GMOM (3 nmol L −1 and 10 nmol L −1 ) was inhibited with dual affinity by (+)-MK-801, (R,S)-ketamine and memantine, in both presence and absence of agonists. [ 3 H]MK-801 (2 nmol L −1 ) was inhibited in a monophasic manner by GMOM under baseline and combined agonist conditions, with an IC 50 value of ~19 nmol L −1 . The non-linear Scatchard plots, biphasic inhibition by open channel blockers, and bi-exponential kinetics of [ 3 H]GMOM indicate a complex mechanism of interaction with the NMDA receptor ionophore. The implications for quantifying the PET signal of [ 11 C]GMOM are discussed.
AB - Labeled with carbon-11, N-(2-chloro-5-thiomethylphenyl)-N′-(3-methoxyphenyl)-N′-methylguanidine ([ 11 C]GMOM) is currently the only positron emission tomography (PET) tracer that has shown selectivity for the ion-channel site of N-methyl-D-aspartate (NMDA) receptors in human imaging studies. The present study reports on the selectivity profile and in vitro binding properties of GMOM. The compound was screened on a panel of 80 targets, and labeled with tritium ([ 3 H]GMOM). The binding properties of [ 3 H]GMOM were compared to those of the reference ion-channel ligand [ 3 H](+)-dizocilpine maleate ([ 3 H]MK-801), in a set of concentration-response, homologous and heterologous inhibition, and association kinetics assays, performed with repeatedly washed rat forebrain preparations. GMOM was at least 70-fold more selective for NMDA receptors compared to all other targets examined. In homologous inhibition and concentration-response assays, the binding of [ 3 H]GMOM was regulated by NMDA receptor agonists, albeit in a less prominent manner compared to [ 3 H]MK-801. Scatchard transformation of homologous inhibition data produced concave upward curves for [ 3 H]GMOM and [ 3 H]MK-801. The radioligands showed bi-exponential association kinetics in the presence of 100 μmol L −1 l-glutamate/30 μmol L −1 glycine. [ 3 H]GMOM (3 nmol L −1 and 10 nmol L −1 ) was inhibited with dual affinity by (+)-MK-801, (R,S)-ketamine and memantine, in both presence and absence of agonists. [ 3 H]MK-801 (2 nmol L −1 ) was inhibited in a monophasic manner by GMOM under baseline and combined agonist conditions, with an IC 50 value of ~19 nmol L −1 . The non-linear Scatchard plots, biphasic inhibition by open channel blockers, and bi-exponential kinetics of [ 3 H]GMOM indicate a complex mechanism of interaction with the NMDA receptor ionophore. The implications for quantifying the PET signal of [ 11 C]GMOM are discussed.
KW - N
KW - NMDA receptor
KW - N′-diaryl-N-methylguanidine
KW - [ H]GMOM
KW - [ H]MK-801
KW - binding
KW - ion-channel
UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85061827710&origin=inward
UR - https://www.ncbi.nlm.nih.gov/pubmed/30784206
U2 - https://doi.org/10.1002/prp2.458
DO - https://doi.org/10.1002/prp2.458
M3 - Article
C2 - 30784206
SN - 2052-1707
VL - 7
JO - Pharmacology research & perspectives
JF - Pharmacology research & perspectives
IS - 1
M1 - e00458
ER -