BDNF and depressive symptom measurement: In a rat chronic unpredictable stress model of depression and anxiety, the expression of glutamate transporter GLT–1 increased in a BDNF–TrkB–dependent manner 24 h after the intraperitoneal administration of a single sub-anesthetic dose of ketamine [128], indicating that GLT–1 is a potential downstream target of BDNF–TrkB signaling, which mediates the antidepressant effect.