[3H]-LY341495 as a novel antagonist radioligand for group II metabotropic glutamate (mGlu) receptors: characterization of binding to membranes of mGlu receptor subtype expressing cells.
Metabotropic glutamate (mGlu) receptors are a family of eight known subtypes termed mGlu1-8. Currently, few ligands are available to study the pharmacology of mGlu receptor subtypes. In functional assays, we previously described LY341495 as a highly potent and selective mGlu2 and mGlu3 receptor antagonist. In this study, radiolabeled [3H]-LY341495 was used to investigate the characteristics of receptor binding to membranes from cells expressing human mGlu receptor subtypes. Using membranes from cells expressing human mGlu2 and mGlu3 receptors, [3H]-LY341495 (1 nM) specific binding was > 90% of total binding. At an approximate K(D) concentration for [3H]-LY341495 binding to human mGlu2 and mGlu3 receptors (1 nM), no appreciable specific binding of [3H-]LY341495 was found in membranes of cells expressing human mGlu1a, mGlu5a, mGlu4a, mGlu6, or mGlu7a receptors. However, modest (approximately 20% of mGlu2/3) specific [3H]-LY341495 (1 nM) binding was observed in human mGlu8 expressing cells. [3H]-LY341495 bound to membranes expressing human mGlu2 and mGlu3 receptors in a reversible and saturable manner with relatively high affinities (Bmax 20.5 +/- 5.4 and 32.0 +/- 7.0 pmol/mg protein; and K(D) = 1.67 +/- 0.20 and 0.75 +/- 0.43 nM, respectively). The pharmacology of [3H]-LY341495 binding in mGlu2 and mGlu3 expressing cells was consistent with that previously described for LY341495 in functional assays. [3H]-LY341495 binding provides a useful way to further investigate regulation of receptor expression and pharmacological properties of mGlu2 and mGlu3 receptor subtypes in recombinant systems.
Johnson
B G
BG
Neuroscience Research, Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
Wright
R A
RA
Arnold
M B
MB
Wheeler
W J
WJ
Ornstein
P L
PL
Schoepp
D D
DD
D000596:Amino Acids / Q000493:pharmacokinetics*; D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000493:pharmacokinetics / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D011869:Radioligand Assay; D018094:Receptors, Metabotropic Glutamate / Q000032:analysis / Q000145:classification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000032:analysis / Q000378:metabolism; D014162:Transfection; D014316:Tritium; D014966:Xanthenes / Q000493:pharmacokinetics*
D000596:Amino Acids; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C114624:LY 341495; D018094:Receptors, Metabotropic Glutamate; D011994:Recombinant Proteins; D014966:Xanthenes; D014316:Tritium; D002118:Calcium