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Lactobacillus reuteri Copyright: Visuals Unlimited/Corbis

The idea that gut microbes can communicate with the brain to change behavior and, correspondingly, that signals from the brain can influence microbial gut populations has been around for a while and most of us in evmed land are pretty convinced by these links. Joe Alcock has written extensively in this area. Another two papers have been published recently that explore this microbiome-brain interaction. The first is published in eLIFE by Gacias et al and titled “Microbiota-driven transcriptional changes in prefrontal cortex override genetic differences in social behavior.” There is a commentary on this paper from Thomas Kuntz and Jack Gilbert, both from the University of Chicago, titled “Does the brain listen to the gut?

The second paper, by Buffington et al, is published in Cell, and titled “Microbial Reconstitution Reverses Maternal Diet-Induced Social and Synaptic Deficits in Offspring.” It also benefits from an easy-to-read commentary in Nature Reviews Neuroscience, called “Making Friends With Microbes”, by Natasha Bray. As Bray explains, Buffington and colleagues showed that maternal obesity, in a mouse model, leads to social and synaptic deficits in the offspring that are caused by a reduction in certain gut-bacterial species. These deficits can be rescued by adding Lactobacillus reuteri to the offsprings’ drinking water. Specifically, baby mice from obese mothers had a ninefold decrease in L. reuteri in their guts and demonstrated measurable social withdrawal. Previous work has shown that the presence of L. reuteri in the gut increases plasma levels of oxytocin, the hormone that is important for social interactions, says Bray. Here, she says, the authors found that oxytocin was expressed in fewer cells in the hypothalamic paraventricular nuclei (PVN) of obese-mothered offspring than of controls and, strikingly, that the addition of L. reuteri to their drinking water increased oxytocin expression in the brain and reversed the social behaviour deficits in the offspring.