Recent progress in the development of mGluR4 positive allosteric modulators for the treatment of Parkinson's disease.

This article describes recent advances in the development and biological evaluation of small molecule mGluR4 positive allosteric modulators (PAMs), and, to a lesser extent, orthosteric agonists. Due to its expression in the basal ganglia, the Family 3 GPCR metabotropic glutamate receptor subtype 4 (mGluR4) has recently garnered a great deal of attention as a putative target for the treatment of Parkinson's disease and a variety of other CNS disorders. Until 2008, with the exception of the prototypical mGluR4 PAM (-)-PHCCC, very few small molecule tools existed to probe the role of selective activation of mGluR4. This review will focus on the explosion of novel mGluR4 PAMs reported in the past year and the further preclinical validation of mGluR4 activation as a potentially groundbreaking treatment for Parkinson's disease.