The endocannabinoidome in neuropsychiatry: Opportunities and potential risks

Pharmacol Res. 2021 Aug;170:105729. doi: 10.1016/j.phrs.2021.105729. Epub 2021 Jun 11.

Abstract

The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.

Keywords: Affective disorders; Bipolar disorder; Depression; Endocannabinoid receptors; Neuro-immune; Neurodegeneration; Neuroscience; Neurotoxicity; Oxidative stress; Psychiatry; Schizophrenia.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology
  • Brain / drug effects
  • Brain / metabolism*
  • Brain / physiopathology
  • Central Nervous System Agents / therapeutic use
  • Endocannabinoids / metabolism*
  • Humans
  • Memory
  • Mental Disorders / drug therapy
  • Mental Disorders / metabolism*
  • Mental Disorders / physiopathology
  • Mental Disorders / psychology
  • Neurodegenerative Diseases / drug therapy
  • Neurodegenerative Diseases / metabolism*
  • Neurodegenerative Diseases / physiopathology
  • Neurodegenerative Diseases / psychology
  • Neuroinflammatory Diseases / drug therapy
  • Neuroinflammatory Diseases / metabolism*
  • Neuroinflammatory Diseases / physiopathology
  • Neuroinflammatory Diseases / psychology
  • Neuronal Plasticity
  • Receptor, Cannabinoid, CB1 / drug effects
  • Receptor, Cannabinoid, CB1 / metabolism*
  • Receptor, Cannabinoid, CB2 / drug effects
  • Receptor, Cannabinoid, CB2 / metabolism*
  • Synaptic Transmission

Substances

  • Anti-Inflammatory Agents
  • Central Nervous System Agents
  • Endocannabinoids
  • Receptor, Cannabinoid, CB1
  • Receptor, Cannabinoid, CB2