GABA Deficits Disturb Endocannabinoid System

Reports new study in Biological Psychiatry

Philadelphia, PA, January 24, 2012 – Changes in the endocannabinoid system may have important implications for psychiatric and addiction disorders. This brain system is responsible for making substances that have effects on brain function which resemble those of cannabis products, e.g., marijuana.

The endocannabinoid system is of particular interest in the field of schizophrenia research because exposure to cannabis products during adolescence and young adulthood appears to increase the risk for developing schizophrenia. Also, in studies examining brain tissue collected from people who had schizophrenia, changes in the endocannabinoid system were highly correlated with changes in the principal inhibitory chemical messenger system in the brain, the gamma-aminobutyric acid (GABA) system.

The current study was conducted in order to research the relationship between changes in the GABA system and changes in the endocannabinoid system. Led by Dr. David Lewis at the University of Pittsburgh, researchers made genetic manipulations in mice that selectively reduced the GABA system function by decreasing the expression of the enzyme that makes GABA, GAD67, or by decreasing the expression of the principal receptor target for endocannabinoids in the brain, the cannabinoid 1 receptor (CB1R), in order to determine whether a change in one is sufficient to cause a change in the other.

Using these techniques, the researchers demonstrated that reduced expression of GAD67 can lead to reduced expression of CB1R, but not vice versa.

“Because activation of the CB1R suppresses GABA release, lower levels of CB1R may help augment GABA release from nerve terminals that have below normal amounts due to reduced GABA synthesis,” said Dr. Lewis of the results. “This evidence suggests that reduced GABA signaling is an ‘upstream’ event in the disease process of schizophrenia and that lower CB1R is a compensation to help normalize GABA signaling.”

These findings indicate that GABA abnormalities in schizophrenia are what trigger the disturbances in the endocannabinoid system. Importantly, cannabis use also alters GABA activity in the brain.

“While the whole story is still developing, from these data, it looks like developmental deficits in GABA systems are sufficient to disturb the function of the endocannabinoid system. This could be an important clue to the link between cannabis use and psychosis,” commented Dr. John Krystal, editor of Biological Psychiatry.

Additional research will be necessary to further explore such links, including investigations into whether and/or how cannabis exposure affects the relationship between GAD67 and CB1R.

The article is “Cortical Glutamic Acid Decarboxylase 67 Deficiency Results in Lower Cannabinoid 1 Receptor Messenger RNA Expression: Implications for Schizophrenia” by Stephen M. Eggan, Matthew S. Lazarus, Samuel R. Stoyak, David W. Volk, Jill R. Glausier, Z. Josh Huang, and David A. Lewis (doi: 10.1016/j.biopsych.2011.09.014). The article appears in Biological Psychiatry, Volume 71, Issue 2 (January 15, 2012), published by Elsevier.

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Notes for editors
Full text of the article is available to credentialed journalists upon request; contact Rhiannon Bugno at +1 214 648 0880 or Biol.Psych@utsouthwestern.edu. Journalists wishing to interview the authors may contact Dr. David Lewis at +1 412 624 3934 or lewisda@upmc.edu.

The authors’ affiliations, and disclosures of financial and conflicts of interests are available in the article.

John H. Krystal, M.D., is Chairman of the Department of Psychiatry at the Yale University School of Medicine and a research psychiatrist at the VA Connecticut Healthcare System. His disclosures of financial and conflicts of interests are available here.

About Biological Psychiatry
Biological Psychiatry is the official journal of the Society of Biological Psychiatry, whose purpose is to promote excellence in scientific research and education in fields that investigate the nature, causes, mechanisms and treatments of disorders of thought, emotion, or behavior. In accord with this mission, this peer-reviewed, rapid-publication, international journal publishes both basic and clinical contributions from all disciplines and research areas relevant to the pathophysiology and treatment of major psychiatric disorders.

The journal publishes novel results of original research which represent an important new lead or significant impact on the field, particularly those addressing genetic and environmental risk factors, neural circuitry and neurochemistry, and important new therapeutic approaches. Reviews and commentaries that focus on topics of current research and interest are also encouraged.

Biological Psychiatry is one of the most selective and highly cited journals in the field of psychiatric neuroscience. It is ranked 4th out of 126 Psychiatry titles and 15th out of 237 Neurosciences titles in the Journal Citations Reports® published by Thomson Reuters. The 2010 Impact Factor for Biological Psychiatry is 8.674.


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Media contact
Rhiannon Bugno
Biological Psychiatry Editorial Office
+1 214 648 0880
biol.psych@utsouthwestern.edu