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. MTEP is a negative allosteric modulator of the mGlu5a receptor subtype (Ki = 42 nM; IC50 = 110 nM). MTEP at 0.3 mg/kg produces antidepressant effects in several rodent models of depression. It also demonstrates neuroprotective potential by preventing excitotoxic neuronal damage when administered through either intrahippocampal or intraperitoneal injection. Additionally, MTEP demonstrates an anxiolytic-like phenotype in rodent models similar to that of benzodiazepines while lacking undesirable sedative and addictive effects.
