Probiotics affect neurochemistry of mice

A short post this one on a piece of research picked up via the Science Daily website and also PopSci amogst others by Bravo and colleagues* published in PNAS on the role of probiotics in moderating behaviour in mice. The paper abstract is here.

I was immediately drawn to this paper because it seemed to tie in perfectly with some research discussed not so long ago on this blog concerning how gut bacteria can affect behaviour (and vice-versa). The difference in the Bravo paper being that not only did supplementation with a probiotic containing Lactobacillus rhamnosus JB-1 seem to affect gut bacterial populations, it also seemed to affect markers of stress and anxiety and the expression of receptors for the neurotransmitter GABA (at least in mice).

There are a few elements of this paper to, pardon the pun, digest.

L.rhamnosus is no stranger to probiotic research and speculation with various strains appearing in quite a few papers as a treatment for anything from dermatitis to diarrhoea (with varying degrees of clinical success).  The current paper suggested that administration affected GABA receptors in parts of the mouse brain thought to be related to anxiety and depression, increasing receptors in some areas and reducing expression in others resulting in reduced anxiety-type behaviours being presented. It also seemed to affect levels of the stress hormone corticosterone involved in the stress response. The question of 'what did what' is a little more complex but at least the results tie in with similar findings using other preparations.

With human beings in mind, one can perhaps see the potential 'applicability' of these findings in both an intervention and exploratory capacity. GABA (and GABA receptors) like other neurotransmitters is found in the gut and as a result must serve some purpose in that vicinity and perhaps beyond. I don't have time to mention all the findings in relation to GABA and autism but there might be some connection there.

The authors in their description of the study describe this as a good example of communication of the gut-brain axis in light of effects only seen when the vagus nerve was intact. I would tend to agree that these findings offer some very, very interesting targets for research on how our gut and brain 'talk' to each other; something that has also been mentioned from time to time in autism and Asperger syndrome also.

The final words however really needs to go to the rising research star that is psychology potentially being mediated by what goes on in our gut and vice-versa.

* Bravo J. et al. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. PNAS. August 2011.