Glutamate, the major excitatory neurotransmitter in the brain, acts on both ionotropic and metabotropic glutamate receptors. Excessive metabotropic glutamate receptor (mGluR) transmission has been linked to epilepsy, ischemia, pain, anxiety, and depression. Eight subtypes (1-
8) and multiple splice variants of the mGluR have been identified and grouped based on their pharmacological properties. Group I mGluRs (subtypes 1 and 5) activate the phosphatidyl inositol pathway, while Group II (2 and 3) and Group III (4, 6, 7 and 8) inhibit adenylyl cyclase. MPEP is a potent, highly selective non-
competitive antagonist at the mGlu5a receptor subtype (IC
50 = 36 nM) while having no agonist or antagonist activities at the mGlu1b receptor at concentrations up to 30 μM.
1 MPEP is centrally active following systemic administration
in vivo, inducing anxiolytic-
like effects in rodent models of anxiety and depression when administered at 1-
30 mg/kg.
1 MPEP has also been reported as a positive allosteric modulator of mGluR4 at μM concentrations.
2