In vitro activity: MPEP is a highly potent, selective, and non-competitive antagonist of mGlu5 receptor with IC50 of 36 nM, it exhibits no appreciable activity at mGlu1b/2/3/4a/7b/8a/6 receptors. MPEP reverses maze learning and PSD-95 deficits in Fmr1 knock-out mice. Unlike the NMDA antagonist MK-801, MPEP does not injure the adult retrosplenial cortex, in which it fails to induce heat shock protein 70 (Hsp70). Moreover, MPEP does not elicit to the same extent as MK-801 apoptosis in cortical areas at perinatal stages, as revealed by caspase 3 expression. These data identify new cellular targets for the anxiolytic and antidepressant effect of MPEP, indicating also in addition that in contrast to MK-801, it lacks the cortical neurotoxicity associated with psychotomimetic side-effects. MPEP has the potential use as anxiolytic/antidepressant drug. MPEP has no appreciable agonist or antagonist activity at the closely related recombinant human mGlu1b receptor expressed in CHO-K1 cells or a purinoreceptor endogenously expressed in L(tk-) cells up to concentrations of 100 μM. Furthermore, MPEP shows no appreciable agonist or antagonist activity in cAMP accumulation or [35S]-GTPγS binding assays at the recombinant human group II and III metabotropic receptors (human mGlu2, -3, -4a, -6, -7b, -8a) as well as the human NMDA (NMDAR1A/2A, -1A/2B), rat AMPA (GluR3) and human kainate (GluR6) receptor subtypes. In slices of rat neonatal hippocampus, striatum, and cortex but not cerebellum, MPEP inhibits DHPG-stimulated PI hydrolysis with IC50 of 8.0 nM, 20.5 nM, and 17.9 nM, respectively. MPEP positively modulates the hmGluR4 in a recombinant expression system, and the effect of MPEP is fully dependent on the activation of the orthosteric agonist L-AP4.

Kinase Assay: MPEP is a highly potent, selective, and non-competitive antagonist of mGlu5 receptor with IC50 of 36 nM, it exhibits no appreciable activity at mGlu1b/2/3/4a/7b/8a/6 receptors.

Cell Assay: In slices of rat neonatal hippocampus, striatum, and cortex but not cerebellum, MPEP inhibits DHPG-stimulated PI hydrolysis with IC50 of 8.0 nM, 20.5 nM, and 17.9 nM, respectively. MPEP positively modulates the hmGluR4 in a recombinant expression system, and the effect of MPEP is fully dependent on the activation of the orthosteric agonist L-AP4.