Microbiome Regulates Fear Response via the Amygdala

MedicalResearch.com Interview with:

Dr. Gerard Clarke PhD APC Microbiome Institute Department of Psychiatry and Neurobehavioural Science University College Cork, Cork, Ireland

Dr. Clarke

Dr. Gerard Clarke PhD
APC Microbiome Institute
Department of Psychiatry and Neurobehavioural Science
University College Cork, Cork, Ireland

MedicalResearch.com: What is the background for this study?

Response: Over the last decade or so, we and others have shown that the gut microbiome exerts a broad influence on the central nervous system, reflected in a range of abnormal behaviours and altered brain function in germ-free animals. These germ-free animals grow up in a sterile bubble and allow us to see what aspects of brain and behaviour could be under the influence of the microorganisms in our gastrointestinal tract.

One of the most consistent findings to emerge relates to anxiety-like behaviours.

MedicalResearch.com: What are the main findings?

Response: The main findings of the current study is that we have now shown the microbiome also regulates the fear response and does so via the amygdala. The amygdala, an almond shaped structure, is the seat of fear and anxiety in the brain. To our knowledge, this is the first direct microbial link to fear pathways and we now know that for normal fear responses, we need to have appropriate microbes in our gut. We have also shown the normal functioning of the amygdala is heavily influenced by the microbiota as it was in a hyperactive state at the molecular level in the germ-free animals and primed to respond to, or process differently, fear-related signals.

MedicalResearch.com: What should readers take away from your report?

Response: Excessive fear responses are challenging to therapeutically manage. If, for example, you have experienced a traumatic event, those memories can be easily triggered and hard to shake. Excessive brain responses to fear memories are manifested in post-traumatic stress disorder (PTSD). Our study offers further support for the possibility that the gut microbiome could in the future be targeted to generate efficacious new treatment options for anxiety disorders such as PTSD. However, it is still early days and caution is advised as we seek to bring this research from bench to bedside.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Response: The results of this study suggest a number of avenues for future research. Firstly, the study was conducted in germ-free animals and apart from the boy in the bubble, there is no real clinical equivalent in terms of a microbe-free human. We need then to establish this is relevant under less extreme conditions. We also need to see how the microbiome is exerting these intriguing effects and find out what are the key signals from the gut to the brain that act to regulate the fear response. This could be down to microbial metabolites but there are also a number of other gut-brain axis routes of communication. Once we have this kind of information, the way could open up to dampen the fear response by targeting the gut microbiome. This includes options such as psychobiotics.

MedicalResearch.com: Is there anything else you would like to add?

Response: This research was supported by Science Foundation Ireland through a centre grant to the APC Microbiome Institute and by the Brain and Behaviour Research Foundation.

MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.


Mol Psychiatry. 2017 May 16. doi: 10.1038/mp.2017.100. [Epub ahead of print]
The microbiome regulates amygdala-dependent fear recall.
Hoban AE1,2, Stilling RM1,2, Moloney G2, Shanahan F1, Dinan TG1,3, Clarke G1,3, Cryan JF1,2.

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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Last Updated on June 1, 2017 by Marie Benz MD FAAD