GRIA1 and major depressive disorder: Opposite to results observed in GluA1, a stress paradigm in a rat model of depression increased hippocampal GluA2 phosphorylation levels, which was partially reduced by acute ketamine administration (65), though some studies showed opposite results where ketamine upregulated GluA2 subunits in both the mPFC and hippocampus of rodents (45, 64).