Article date: February 1998
By: Jayne Cartmell, Geo Adam, Sylvie Chaboz, Robert Henningsen, John A. Kemp, Agnes Klingelschmidt, Veit Metzler, Frederick Monsma, Hervé Schaffhauser, Jürgen Wichmann, Vincent Mutel, in Volume 123, Issue 3, pages 497-504
The binding of the new selective group II metabotropic glutamate receptor radioligand, [3H]‐(2S,2′R,3′R)‐2‐(2′,3′‐dicarboxycyclopropyl)glycine ([3H]‐DCG IV), was characterized in rat mGlu2 receptor‐transfected CHO cell membranes.
[3H]‐DCG IV binding was pH‐dependent, but was not sensitive to temperature. Saturation analysis showed the presence of a single binding site, with a Kd value of 160 nM and a Bmax value of 10 pmol mg−1 protein. Binding was not sensitive to Na+‐dependent glutamate uptake blockers or Cl−‐dependent glutamate binding inhibitors. Furthermore, up to concentrations of 1 mM, the glutamate ionotropic receptor agonists, N‐methyl‐D‐aspartic acid (NMDA), (S)‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) and kainate, did not affect [3H]‐DCG IV binding.
Of the compounds observed to inhibit [3H]‐DCG IV binding, the most potent were the recently described selective group II agonist, (+)‐2‐aminobicyclo‐[3.1.0]hexane‐2,6‐dicarboxylate (LY 354740; Ki value 16 nM) and antagonist, 2‐amino‐2‐(2‐carboxycyclopropan‐1‐yl)‐3‐(dibenzopyran‐4‐yl) propanoic acid (LY 341495; Ki value 19 nM). As expected, for a G‐protein‐coupled receptor, guanosine‐5′‐O‐(3‐thiotriphosphate) (GTPγS) inhibited [3H]‐DCG IV binding in a concentration‐dependent manner, with an IC50 value of 12 nM.
A highly significant correlation was observed between the potencies of compounds able to inhibit [3H]‐DCG IV binding and potencies obtained for agonist activity in a GTPγ35S binding functional assay. In addition, these studies identified a number of compounds with previously unknown activity at mGlu2 receptors, including L(+)‐2‐amino‐3‐phosphonopropionic acid (L‐AP3), L(+)‐2‐amino‐5‐phosphonopentanoic acid (L‐AP5), 3‐((RS)‐2‐carboxypiperazin‐4‐yl)‐propyl‐1‐phosphonic acid (R‐CPP), N‐acetyl‐L‐aspartyl‐L‐glutamic acid (NAAG) and (RS)‐α‐methylserine‐O‐phosphate (MSOP).
The binding of the new selective group II metabotropic glutamate receptor radioligand, [3H]‐(2S,2′R,3′R)‐2‐(2′,3′‐dicarboxycyclopropyl)glycine ([3H]‐DCG IV), was characterized in rat mGlu2 receptor‐transfected CHO cell membranes.
[3H]‐DCG IV binding was pH‐dependent, but was not sensitive to temperature. Saturation analysis showed the presence of a single binding site, with a Kd value of 160 nM and a Bmax value of 10 pmol mg−1 protein. Binding was not sensitive to Na+‐dependent glutamate uptake blockers or Cl−‐dependent glutamate binding inhibitors. Furthermore, up to concentrations of 1 mM, the glutamate ionotropic receptor agonists, N‐methyl‐D‐aspartic acid (NMDA), (S)‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) and kainate, did not affect [3H]‐DCG IV binding.
Of the compounds observed to inhibit [3H]‐DCG IV binding, the most potent were the recently described selective group II agonist, (+)‐2‐aminobicyclo‐[3.1.0]hexane‐2,6‐dicarboxylate (LY 354740; Ki value 16 nM) and antagonist, 2‐amino‐2‐(2‐carboxycyclopropan‐1‐yl)‐3‐(dibenzopyran‐4‐yl) propanoic acid (LY 341495; Ki value 19 nM). As expected, for a G‐protein‐coupled receptor, guanosine‐5′‐O‐(3‐thiotriphosphate) (GTPγS) inhibited [3H]‐DCG IV binding in a concentration‐dependent manner, with an IC50 value of 12 nM.
A highly significant correlation was observed between the potencies of compounds able to inhibit [3H]‐DCG IV binding and potencies obtained for agonist activity in a GTPγ35S binding functional assay. In addition, these studies identified a number of compounds with previously unknown activity at mGlu2 receptors, including L(+)‐2‐amino‐3‐phosphonopropionic acid (L‐AP3), L(+)‐2‐amino‐5‐phosphonopentanoic acid (L‐AP5), 3‐((RS)‐2‐carboxypiperazin‐4‐yl)‐propyl‐1‐phosphonic acid (R‐CPP), N‐acetyl‐L‐aspartyl‐L‐glutamic acid (NAAG) and (RS)‐α‐methylserine‐O‐phosphate (MSOP).
British Journal of Pharmacology (1998) 123, 497–504; doi:10.1038/sj.bjp.0701647
DOI: 10.1038/sj.bjp.0701647
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