More recently it was shown that local infusion of ketamine in the LHb blocks burst-firing activity and induces antidepressant-like responses in an animal model of depression (Shepard et al., 2018; Yang et al., 2018) and that ketamine-induced Hb changes are modulated by opioid receptors (Klein et al., 2020). This evidence concerns the gene GSTM1 and depressive disorder.