GRM5 and fragile X syndrome: Chemical compounds targeting metabotropic glutamate receptor 5 (mGluR5) and other neurotransmitter receptors such as γ-aminobutyric acid and serotonin receptors4, 5 or downstream signaling pathways such as mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK)1/2 and phosphatidylinositol 3 kinase (PI3K)/glycogen synthase kinase 3β/Akt6 have been tested for their ability to improve FXS symptoms such as anxiety, seizure, and hyperactivity.