The role of sigma receptors in depression

Behavioral models used to test potential antidepressants have shown that ligands that bind to sigma receptors possess "antidepressant-like" properties. The focus of this review is to discuss the literature concerning sigma receptors and their ligands, with respect to their antidepressants properties. In addition to the behavioral data, we discuss electrophysiological and biochemical models demonstrating sigma receptors' ability to modulate important factors in the pathophysiology of depression and/or the mechanisms of action of antidepressants such as the serotonergic neurotransmission in the dorsal raphe nucleus (DRN) and the glutamatergic transmission in the hippocampus. We also discuss the significance of these two systems in the mechanism of action of antidepressants. Sigma ligands have potential as antidepressant medications with a fast onset of action as they produce a rapid modulation of the serotonergic system in the DRN and the glutamatergic transmission in the hippocampus. As these effects of sigma ligands may produce antidepressant properties by completely novel mechanisms of action, they may provide an alternative to the antidepressants currently available and may prove to be beneficial for treatment-resistant depressed patients.