Future avenues for drug treatment of dyskinesia include the development of adenosine A2A receptor antagonists [227,228] as well as the use of metabotropic glutamate receptor 5 (mGluR5) antagonists [229] and orthosteric metabotropic glutamate receptor 4 (mGluR4) agonists [230]. This evidence concerns the gene GRM4 and drug-induced dyskinesia.