Skip to main content

Gut-Brain Axis

By
The papers for this week aimed to investigate the role of the gut-brain axis in stress and neurodevelopmental disorders. While we know that our microbiome influences brain function and certainly has some down-stream effects on behavior, the exact mechanisms by which this happens are complex and still not fully understood. 

Reber et al. demonstrated that immunization with an immunoregulatory environmental microorganism (M. vaccae) can rescue a stress phenotype induced with subordinate colony housing. I found the data in this paper very compelling, and the data clearly shows that immunized mice exhibit many more “proactive” behaviors than non-immunized mice, but I did wonder if there was a way to get a more complete picture of dominance status. Here, they compared the number of proactive behaviors (attacks, chasing) to reactive behaviors (flight, avoiding), to determine the dominance score of every animal. However, they only did this with male mice with other male aggressors, and I felt that their definition of proactive behaviors was incomplete. For instance, could they have monitored the vocalizations of the mice, or perhaps motion tracking? Also, what would the data look like if the aggressor was a lactating female? 

The second paper, by Buffington et al., examined the correlation between maternal obesity and neurodevelopmental disorders in offspring, particularly with respect to autism. Most interestingly, pairing MHFD (maternal high-fat diet) mice with MRD (maternal regular diet) mice restores the microbiome of the MHFD mice, and ultimately improves their social behavior. They also repeated a similar experiment by re-introducing L. reuteri into the microbial landscape of MHFD mice, which promotes oxytocin levels and therefore plays an important role in social behaviors. What I found interesting is that re-introducing L. reuteri had no effect on repetitive behaviors or anxiety of the mice (as exemplified in the marble burying paradigm), and only altered the social behavior of the mice. Does this in fact suggest that repetitive behaviors are not dependent on the microbiome? I certainly would have expected anxious behaviors to be influenced by the microbiome, so I would have liked to see a more detailed analysis of this

Comments

Post a Comment

Popular posts from this blog

Gut-Brain Interactions: Buffington et al, Reber et al 2016

By
April 13 Papers (Buffington et. al, Reber et. al) I found this week’s papers to be quite novel in that they both proposed potential treatments for neurodevelopmental or psychiatric disorders that target bacterial or microbial abnormalities and how these give rise to certain behavioral and physical symptoms associated with the disorders. I thought this was a very unusual yet interesting approach, and as I have not previously studied the gut-brain axis, these papers offered me a fresh perspective on researching psychiatric and neurodevelopmental disorders. They were also unconventional in their focus of the physical symptoms that often accompany mental disorders, as this is not something that I have seen many other papers touch upon very much. Particularly, I was surprised by the Reber et al paper’s focus on the link between psychiatric disorders and inflammation in organs other than the brain, such as the colon, and the Buffington et al paper’s description of a relationship between ...
Post a Comment
Read more

Gut-brain axis

By
This weeks papers Reber et al. 2016 and Buffington et al. 2016 present a super interesting look into the gut-brain axis. Regarding both of these papers, it was amazing to see how potent favorable or unfavorable gut microbiome compositions are in affecting neuronal signaling and overall behavior. Reber et al. shows how immunoregulatory immunization with specifically heat killed M.vaccae can serve as a protective factor against chronic subordinate stress induce colotis as well as behavioral symptoms due to chronic stress as such. Interestringly, this paper depleted regulatory T cell activity via the anti CD25 antibody in order to show that the antiinflammatory mechanism induced by m vaccae immunization is depented on the secondary regulatory mechanisms offered by Treg proliferation and signaling. But, when T reg signaling was removed, this did not seem to cause a significant change in behavior . Therefore, this begs the consideration of what othe rmechanisms may be at play in order ...
Post a Comment
Read more

Ramirez et al.: 2013 and 2015 Papers

By
In these papers, Ramirez et al. strive to understand how memory encoding via optogenetic manipulation of engram-bearing cells in the hippocampus, specifically the dentate gyrus, can affect an animal’s response to a stressful context.  The first paper, published in 2013, was crucial to the field as it introduced this very exciting technique; in this paper, Ramirez et al. use tet-tag to manipulate brain circuity and establish associations between two contexts. Throughout the paper, this is referred to as “false memories.” Using these artificial memories, the investigators are able to manipulate the animal’s fear response in a specific context. Specifically, after the animals are conditioned to a repeated fearful stimulus (a foot shock, in context B), activation of the involved DG cells in a different context (context A’) will also initiate a fear response (in absence of any foot shock). In this experiment, the false memory is used to create an unnatural fear association in a given...
Post a Comment
Read more