MPEP

Administered intraperitoneally (i.p.) or perorally (p.o.) at 60 minutes before the tests

2-methyl-6-(2-phenylethynyl)pyridine

ca.30 mg/kg

Suspended in a 1% aqueous solution of Tween 80

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 uM. Furthermore, MPEP shows no appreciable agonist or antagonist activity in cAMP accumulation or [35S]-GTPgammaS 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. [1] 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. [3]

PI hydrolysis assay, MPEP is tested for antagonist activity at cloned human mGlu5a receptors expressed in L(tk-) cells. Clonal cell lines expressing human mGluR5 receptors are seeded in 24-well tissue culture plates. Cells are labeled to equilibrium with 2 uCi/ml myo-[3H]inositol for 20 hours in Dulbecco's modified Eagle's medium, washed twice in Krebs-Henseleit buffer, and incubated for 30 minutes at room temperature. Subsequently, cells are washed in buffer containing 10 mM LiCl and incubated in the same medium for 20 minutes at 37 C. After aspiration of medium, increasing concentration of MPEP is added to triplicate wells. For test of antagonist activity, a submaximal concentration of quisqualate (0.3 uM) is added immediately after application of MPEP. The reaction is stopped after an incubation of 20 minutes at 37 C by aspiration of the medium and lysis of the cells with 0.75 mL of ice-cold 10 mM formic acid (pH 3). After 30 minutes the extract is diluted into 2 mL of 5 mM NH3solution (yielding a final pH of 8-9) and applied to a column containing DOWEX-1, 8. After flow-through of the extract, columns are washed with 10 mL of H2O and 6 mL of 5 mM sodium tetraborate, 60 mM sodium formate, respectively. Inositol monophosphates are eluted with 6 mL of 100 mM formic acid, 200 mM ammonium formate. The eluted samples are counted 7 hours after addition of 15 mL Irgasave Plus scintillation cocktail in a Tricarb 2700tr counter.

MPEP Chemical Structure

2 years -20CPowder, 2 weeks4Cin DMSO, 2 months-80Cin DMSO