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Animal Study Suggests Link Between Immune Response and Depression

Researchers have found tantalizing evidence as to how flu can trigger depression symptoms.

Vanderbilt scientists believe depression may be triggered by the same mechanisms that enable the immune system to respond to infection.

In a study in the December issue of Neuropsychopharmacology, Chong-Bin Zhu, M.D., Ph.D., Randy Blakely, Ph.D., William Hewlett, M.D., Ph.D., and colleagues activated the immune system in mice to produce “despair-like” behavior that has similarities to depression in humans.

“Many people exhibit signs of lethargy and depressed mood during flu-like illnesses,” said Blakely.

“Generally these have been treated as just a consequence of being physically ill, but we think there is likely to be something more brain-centric at work here.”

Blakely and his colleagues previously reported that inflammatory cytokines can enhance the activity of the serotonin transporter (SERT), which regulates the supply of the neurotransmitter serotonin in the synapse, or gap between nerve cells.

Elevations in SERT activity remove serotonin from brain synapses at an enhanced rate and, based on studies in animal models and man, would be predicted to increase the risk for mood and anxiety disorders. Indeed, a class of antidepressant drugs called selective serotonin reuptake inhibitors (SSRIs) – Prozac, Zoloft, etc. – work by blocking the ability of SERT to eliminate serotonin.

In the current study in mice, the researchers triggered pro-inflammatory cytokine production. Within 30 to 60 minutes, SERT was activated in the brain and the animals displayed despair-like behavior.

Remarkably, this behavior was not observed when cytokine production was triggered in mice lacking the SERT gene. Similarly, a drug that blocks inflammatory molecule signaling also prevented stimulation of SERT and the despair behavior. “It’s as if these inflammatory molecules are an ‘anti-Prozac,'” Blakely said.

In their paper, the researchers cautioned that “we do not presume that changes in SERT activity alone are sufficient to induce the full spectrum of depression traits, nor that our animal model can reproduce all the elements of a complex neuropsychiatric disorder.”

“Nonetheless, we were able to identify a mechanism that may be engaged, even without inflammation, to impact risk for depressive illness,” Blakely said.

More study is needed, researchers said. Identifying genetic variations in the SERT activation pathway, for example, might suggest additional sources of genetic risk for depression.

“Our work suggests that novel therapies targeting inflammation-linked pathways may be of use in the treatment of mood disorders,” he said.

Source: Vanderbilt University Medical Center

Animal Study Suggests Link Between Immune Response and Depression

Rick Nauert PhD

Rick Nauert, PhDDr. Rick Nauert has over 25 years experience in clinical, administrative and academic healthcare. He is currently an associate professor for Rocky Mountain University of Health Professionals doctoral program in health promotion and wellness. Dr. Nauert began his career as a clinical physical therapist and served as a regional manager for a publicly traded multidisciplinary rehabilitation agency for 12 years. He has masters degrees in health-fitness management and healthcare administration and a doctoral degree from The University of Texas at Austin focused on health care informatics, health administration, health education and health policy. His research efforts included the area of telehealth with a specialty in disease management.

APA Reference
Nauert PhD, R. (2015). Animal Study Suggests Link Between Immune Response and Depression. Psych Central. Retrieved on November 19, 2018, from https://psychcentral.com/news/2010/12/21/animal-study-suggests-link-between-immune-response-and-depression/22019.html

 

Scientifically Reviewed
Last updated: 6 Oct 2015
Last reviewed: By John M. Grohol, Psy.D. on 6 Oct 2015
Published on PsychCentral.com. All rights reserved.