GRM5 and depressive disorder: mGluR5 is densely expressed in the mPFC, and expression levels in the mPFC are altered in conditions of chronic pain or depressive disorders (Matosin et al., 2014; DeLorenzo et al., 2015; Lee K.W. et al., 2015; Chung et al., 2017; Esterlis et al., 2017).