Skip to main content

Depression-Related Behaviors, Tye and Chaudhury

By

Both Tye et al and Chaudhury et al saw robust results from activating and inactivating the VTA in depression-related behaviors. I think their findings are both elegantly done and contribute to a bigger story of the VTA and its involvement in mediating behaviors associated with depression. Tye et al show that by inhibiting VTA neurons after Chronic Mild Stress, depressive-like behaviors are induced. By activating the same subset of neurons, escape behaviors after CMS can be restored. Additionally, Tye et al showed that activation of the VTA in rats increases the prevalence of escape behavior in a novel stress test. Chaudhury et al utilize a different stress paradigm called the social defeat stress model. Their data indicate that phasic stimulation of the VTA causes depressive-liked behaviors in a social defeat paradigm, but inhibiting the VTA can restore social interaction in mice after they experience social defeat.

 Each paper explores related, yet different concepts. Although they come to different conclusions when activating and inactivating the VTA, I think the data are still complementary. While Tye et al mainly study stress models that display escape behavior, Chaudhury et al use a stress model that studies social interaction. Both behavioral paradigms are categorized under “Chronic Mild Stress,” yet they are testing two separate aspects that are seen in depression. The overlapping behavior test between the two papers, the sucrose-preference test, examines the anhedonic phenotype under two different conditions: social stress and learned helplessness. This could explain why they see differential results.

Chaudhury et al go a step further in studying the VTA by isolating specific projection routes of the VTA. While their data give great insight into how the VTA-NAc and VTA-mPFC circuits may modulate depressive-like behavior, it’s difficult to believe their interpretation of the results. This is because (a) they only studied male mice and (b) many other known outputs of the VTA are ignored. While their paper offers promising results for interpreting the functional importance of individual VTA circuits, I am still skeptical about there being other factors that may have led to the results they saw.

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