Glutamate Efflux across the Blood-Brain Barrier: New Perspectives on the Relationship between Depression and the Glutamatergic System

Abstract

Depression is a significant cause of disability and affects millions worldwide; however, antidepressant therapies often fail or are inadequate. Current medications for treating major depressive disorder can take weeks or months to reach efficacy, have troubling side effects, and are limited in their long-term capabilities. Recent studies have identified a new set of glutamate-based approaches, such as blood glutamate scavengers, which have the potential to provide alternatives to traditional antidepressants. In this review, we hypothesize as to the involvement of the glutamate system in the development of depression. We identify the mechanisms underlying glutamate dysregulation, offering new perspectives on the therapeutic modalities of depression with a focus on its relationship to blood-brain barrier (BBB) permeability. Ultimately, we conclude that in diseases with impaired BBB permeability, such as depression following stroke or traumatic brain injury, or in neurogenerative diseases, the glutamate system should be considered as a pathway to treatment. We propose that drugs such as blood glutamate scavengers should be further studied for treatment of these conditions.

Keywords: blood glutamate scavengers; blood–brain barrier; depression; glutamate.

Figure 1

Brain-blood glutamate equilibrium: (a). Homeostasis of the normal physiological state. (b). Imbalanced glutamate under pathological conditions and disruption of BBB integrity. 10–100*µM/L The concentration of brain glutamate depends on the degree of disruption of BBB integrity.

Figure 2

The relationship between conditions that disrupt the blood–brain-barrier, glutamate and depression.