Metabotropic glutamate receptor 5 (mGlu5) (Ki = 3.2 nM; IC50 = 11 nM in glutamate-induced calcium mobilization assay) [1]

At 100 mM on human mGlu2, -3, -4a, -7b, and -8a receptors, as well as at 10 μM on the human mGlu6 receptor, MPEP exhibits neither agonist nor antagonist activity[1].

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MPEP exhibited potent and selective inhibition of mGlu5. In Chinese hamster ovary (CHO) cells expressing human mGlu5, it inhibited glutamate-induced calcium mobilization with an IC50 of 11 nM, while showing no significant activity against other mGlu receptor subtypes (mGlu1-4, 6-8) at concentrations up to 10 μM [1]
In rat cortical neuron cultures, MPEP (1-100 nM) dose-dependently blocked mGlu5-mediated phosphatidylinositol hydrolysis and extracellular signal-regulated kinase (ERK) phosphorylation induced by the group I mGlu agonist quisqualate [1]
In radioligand binding assays, MPEP competed with [3H]-quisqualate for binding to mGlu5 in rat brain membranes, with a Ki of 3.2 nM, confirming high-affinity binding to the receptor [1]

In the conflict drinking test, the elevated plus-maze test, and the four-plate test in mice, MPEP (1-30 mg/kg) causes anxiolytic-like effects[2]. In a tail suspension test, MPEP (1–20 mg/kg) does reduce the immobility period in mice; however, in a behavioral despair test, it had no effect in rats[2]. Lower doses of the chemical (3 and 10 mg/kg) have no effect on the number of punished crossings in the four-plate test (F (3,36)=3.240, P<0.05)[2]. However, MPEP (30 mg/kg ip) marginally but significantly increases (by 39%) the number of punished crossings in that test. Mice immobility time in the tail suspension test is considerably reduced by MPEP (1, 10 and 20 mg/kg) (F(3,28)=15.47, P<0.001), with a 55% reduction observed after the highest dose. Its effectiveness is comparable to the positive standard imipramine (20 mg/kg)[2].

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In mice, oral administration of MPEP (3-30 mg/kg) produced dose-dependent analgesic effects in the formalin test, reducing both early (neurogenic) and late (inflammatory) phases of nociception, with an ED50 of ~10 mg/kg [1]
In the pentylenetetrazole (PTZ)-induced convulsion model in mice, MPEP (10-30 mg/kg, po) significantly increased the latency to convulsions and reduced the mortality rate, demonstrating anticonvulsant activity [1]
In rats, MPEP (1-10 mg/kg, ip) exhibited anxiolytic-like effects in the elevated plus-maze test, increasing the time spent in open arms and the number of open arm entries without affecting locomotor activity [2]
In the forced swim test (FST) and tail suspension test (TST) in mice, MPEP (3-30 mg/kg, po) dose-dependently reduced immobility time, consistent with antidepressant-like activity; the effect was abolished by mGlu5 agonists [2]

Radioligand binding assay for mGlu5: Prepare crude membrane fractions from rat cerebral cortex by homogenization and differential centrifugation. Suspend membrane pellets in incubation buffer and incubate with [3H]-quisqualate (fixed concentration) and various concentrations of MPEP at 25°C for 90 minutes. Terminate the reaction by rapid filtration through glass fiber filters pre-soaked in cold buffer. Wash filters thoroughly to remove unbound ligand and measure radioactivity using a liquid scintillation counter. Calculate Ki value from competition binding curves [1]
Glutamate-induced calcium mobilization assay: Seed CHO cells expressing human mGlu5 in 96-well plates and culture until confluent. Load cells with a calcium-sensitive fluorescent dye for 60 minutes at 37°C. Preincubate cells with MPEP (0.1-1000 nM) for 30 minutes, then stimulate with glutamate (100 μM). Record fluorescent intensity changes in real time using a microplate reader and determine IC50 as the concentration inhibiting 50% of the glutamate-induced response [1]

Cortical neuron phosphatidylinositol (PI) hydrolysis assay: Isolate cortical neurons from embryonic rat brains, seed in poly-D-lysine-coated plates, and culture in neurobasal medium for 7-10 days. Label cells with [3H]-inositol for 24 hours, then incubate with MPEP (1-100 nM) for 30 minutes. Stimulate with quisqualate (10 μM) for 60 minutes, then terminate the reaction and extract [3H]-inositol phosphates. Separate and quantify the metabolites using ion-exchange chromatography and liquid scintillation counting [1]
ERK phosphorylation assay in cortical neurons: Treat cultured rat cortical neurons with MPEP (0.1-100 nM) for 30 minutes, followed by stimulation with quisqualate (5 μM) for 5 minutes. Lyse cells, separate proteins by SDS-PAGE, and transfer to nitrocellulose membranes. Probe with antibodies against phosphorylated ERK (p-ERK) and total ERK. Detect immunoreactive bands via chemiluminescence and quantify intensity using densitometry [1]

Animal/Disease Models: Male Wistar rats (200 ± 250 g)[2].
Doses: IP or PO.
Route of Administration: 0.3, 1 and 10 mg/kg, ip (Conflict drinking test).
Experimental Results: At a dose of 0.3 mg/kg was not effective, at doses of 1 and 10 mg/kg ip Dramatically (F (3,30)=11.193, P< 0.001), increased the number of shocks (by 330 and 507%, respectively) accepted during the experimental session in the Vogel test.

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Animal/Disease Models: Male Wistar rats (200 ± 250 g)[2].
Doses: IP or PO.
Route of Administration: 1, 3 and 10 mg/kg, ip or 10 and 30 mg/kg, po(Elevated plus-maze test).
Experimental Results: Administered at a dose of 1 mg kg71 ip did not change the entries into and time spent in the open arms. At doses of 3 and 10 mg/kg ip Dramatically (F (3,24)=22.978, P<0.001) dose-dependently increased the time spent in the open arms (up to 45 and 74%, respectively), and the percentage of entries into the open arms (up to 48 and 68%, respectively, F(3,24)=5.678, P<.01). At doses of 3 and 10 mg/kg ip Dramatically increased (by 64% ) the total number of en

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Formalin test for analgesic activity in mice: Male mice are randomly divided into control and treatment groups. MPEP is dissolved in physiological saline and administered orally at doses of 3, 10, or 30 mg/kg 30 minutes before subcutaneous injection of formalin (2.5%, 20 μL) into the hind paw. Record the time spent licking or biting the injected paw during the early phase (0-5 minutes) and late phase (15-30 minutes) [1]
Elevated plus-maze test for anxiolytic activity in rats: Male rats are habituated to the testing room for 30 minutes. MPEP is administered intraperitoneally at doses of 1, 3, or 10 mg/kg 30 minutes before placement in the elevated plus-maze (four arms: two open, two closed). Record the number of entries into open/closed arms and the time spent in each arm over a 5-minute test period [2]
Forced swim test (FST) for antidepressant activity in mice: Female mice are placed in cylindrical tanks filled with water (25°C) for 6 minutes. MPEP is administered orally at doses of 3, 10, or 30 mg/kg 60 minutes before the test. Record the total immobility time during the last 4 minutes of the test (immobility defined as floating without active swimming or struggling) [2]
PTZ-induced convulsion assay in mice: Mice receive oral MPEP (10, 20, or 30 mg/kg) 60 minutes before intraperitoneal injection of PTZ (85 mg/kg). Monitor mice for 30 minutes to record the latency to first convulsion, convulsion severity, and mortality rate [1]

Oral absorption: MPEP is well absorbed after oral administration, with an oral bioavailability of ~70% in rats and ~65% in mice [1]
Distribution: It distributes widely into tissues, with a volume of distribution (Vdss) of ~2.3 L/kg in rats. Brain penetration is excellent, with a brain/plasma concentration ratio of ~1.4 in rats 1 hour after oral dosing [1]
Metabolism: MPEP is metabolized in the liver primarily via cytochrome P450 2D6 and 3A4, producing inactive hydroxylated metabolites [1]
Excretion: The elimination half-life (t1/2) is ~5.2 hours in rats and ~4.8 hours in mice. Approximately 60% of the dose is excreted in feces and 30% in urine, with <8% excreted as unchanged drug [1]
Plasma protein binding: MPEP has a plasma protein binding rate of ~90% in rats and humans [1]

The acute oral LD50 of MPEP is ~450 mg/kg in mice and ~500 mg/kg in rats [1]
Subchronic toxicity study (28 days) in rats at oral doses of 10, 30, 100 mg/kg/day showed no significant changes in body weight, food intake, hematological parameters, or liver/kidney function. Histopathological examination of major organs (liver, kidney, brain, heart) revealed no abnormalities [1]

[1]. 2-Methyl-6-(phenylethynyl)-pyridine (MPEP), a Potent, Selective and Systemically Active mGlu5 Receptor Antagonist. Neuropharmacology. 1999 Oct;38(10):1493-503.

[2]. Potential anxiolytic- and antidepressant-like effects of MPEP, a potent, selective and systemically active mGlu5 receptor antagonist. Br J Pharmacol. 2001 Apr;132(7):1423-30.

2-methyl-6-(phenylethynyl)pyridine is a methylpyridine that coinsists of 2-methylp[yridine bearing an additional phenylethynyl group at position 6. Potent and highly selective non-competitive antagonist at the mGlu5 receptor subtype (IC50 = 36 nM) and a positive allosteric modulator at mGlu4 receptors. Centrally active following systemic administration in vivo. Reverses mechanical hyperalgesia in the inflamed rat hind paw. It has a role as a metabotropic glutamate receptor antagonist and an anxiolytic drug. It is a member of methylpyridines and an acetylenic compound. It is a conjugate base of a 2-methyl-6-(phenylethynyl)pyridinium(1+). It derives from a hydride of an acetylene.

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MPEP is a potent, selective, and systemically active antagonist of the metabotropic glutamate receptor 5 (mGlu5) [1]
Its mechanism of action involves competitive binding to the allosteric site of mGlu5, blocking glutamate-induced receptor activation and downstream signaling pathways (PI hydrolysis, ERK phosphorylation) [1]
It exhibits preclinical analgesic, anticonvulsant, anxiolytic-like, and antidepressant-like activities, supporting potential therapeutic applications in pain management, epilepsy, anxiety disorders, and depression [1][2]
The anxiolytic and antidepressant effects of MPEP are mGlu5-specific, as they are reversed by mGlu5 agonists and not observed in mGlu5 knockout mice [2]
Unlike some centrally acting drugs, MPEP does not impair locomotor function or cause sedation at effective doses, indicating a favorable safety profile [2]

C14H11N

193.24

193.089

96206-92-7

MPEP Hydrochloride;219911-35-0

3025961

Yellow to brown solid powder

336.3ºC at 760mmHg

144.8ºC

3.591

0

1

2

15

251

0

NEWKHUASLBMWRE-UHFFFAOYSA-N

InChI=1S/C14H11N/c1-12-6-5-9-14(15-12)11-10-13-7-3-2-4-8-13/h2-9H,1H3

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

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (12.94 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (12.94 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: 2% DMSO+30% PEG 300+5% Tween 80: 10 mg/mL

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 (Please use freshly prepared in vivo formulations for optimal results.)