The Potential Role of Cannabinoids in Modulating Serotonergic Signaling by Their Influence on Tryptophan Metabolism

Abstract Phytocannabinoids present in Cannabis plants are well known to exert potent anti-inflammatory and immunomodulatory effects. Previously, we have demonstrated that the psychoactive Δ9-tetrahydrocannabinol (THC) and the non-psychotropic cannabidiol (CBD) modulate mitogen-induced Th1-type immune responses in peripheral blood mononuclear cells (PBMC). The suppressive effect of both cannabinoids on mitogen-induced tryptophan degradation mediated by indoleamine-2,3-dioxygenase (IDO), suggests an additional mechanism by which antidepressive effects of cannabinoids might be linked to the serotonergic system. Here, we will review the role of tryptophan