Characterization of [H-3]-LY354740 binding to rat mGlu2 and mGlu3 receptors expressed in CHO cells using Semliki Forest virus vectors

The binding properties of [H-3]-LY354740 were characterized on rat metabotr opic glutamate receptors mGlu2 and mGlu3 expressed in Chinese hamster ovary (CHO) cells using Semliki Forest virus vectors. The saturation isotherm ga ve K-D values of 20+/-5 and 53+/-8 nM and B-max values of 474+/-261 and 667 +/-89 fmol/mg protein for mGlu2 and mGlu3 receptors, respectively. NMDA, Ca Cl2, DHPG and kainate were inactive up to 1 mM, whereas LY341495, DCG IV an d ibotenate inhibited [H-3]-LY354740 binding with similar potencies on both receptors. L-CCG I, L-AP4, L-AP5, LY354740 and 1S,3R-ACPD were 2- to 4-fol d more potent inhibitors of [H-3]-LY354740 binding to mGlu2 than mGlu3 rece ptors. However, MPPG and L-AP3 had a 6-fold and DTT a 28-fold preference fo r mGlu2 over mGlu3. ZnCl2, at 10 mM: inhibited more than 70% of [H-3]-LY354 740 binding to mGlu2 receptors. At the same concentration it did not affect significantly [H-3]-LY354740 binding to mGlu3 receptors. On the contrary, glutamate, quisqualate, EGLU and NAAG showed a 3, 5-, 7- and 12-fold prefer ence for mGlu3 over mGlu2, Finally, GTP gamma S, which partially inhibited the binding on mGlu2 receptors, was inactive to inhibit [H-3]-LY354740 bind ing on mGlu3 receptors. (C) 2000 Elsevier Science Ltd. All rights reserved.