We propose to expand our previous findings on the efficacy of glutamatergic modulators in patients with unipolar and bipolar depression by testing a specific, new mechanism where by we use ceftriaxone to chronically increase the expression of the glutamate transporter GLT1 in order to facilitate the removal of glutamate from the synaptic cleft in an effort to reduce excessive glutamate transmission and as a result produce acute antidepressant effects. The model presented here is a clinical testable one, and one that, if successful, holds the potential to develop a group of novel pharmacological treatments for major depression.