I’ve mentioned here before the ongoing research on the menagerie of micro-organisms that call us home; the National Institutes of Health is sponsoring the Human Microbiome Project, which is attempting to identify and classify these organisms (which outnumber our own cells by about 10:1), and their roles. We’ve also seen that disruption of the normal microbial population of the digestive tract can cause some serious health problems.
The Science Now site has a report that some new research suggests that changes in the digestive system’s microbiome can affect how the brain works. It has been hypothesized that neurological functions might be affected by toxins produced by bacteria, or by the effect of microbes on the immune system, but this new work seems to suggest a more direct effect.
Now, a new study suggests that gut bacteria can even mess with the mind, altering brain chemistry and changing mood and behavior.
To test for an effect, John Cryan, a neuroscientist at University College Cork in Ireland,and a group of researchers from McMaster University in Canada, fed laboratory mice a broth containing Lactobacillus rhamnosus, a benign bacterium. The particular species was handy, but is also of potential interest because other bacteria from the genus Lactobacillus are common in probiotic preparations. Compared to a control group of mice that received broth without the added bacteria, the treated mice showed lower levels of stress and anxiety.
Mice whose diets were supplemented with L. rhamnosus for 6 weeks exhibited fewer signs of stress and anxiety in standard lab tests, Cryan and colleagues report online today in the Proceedings of the National Academy of Sciences [abstract].
The research team found some evidence that the effect was due, at least in part, to a change in the receptors for GABA [gamma-Aminobutyric acid], an important inhibitory neurotransmitter.
In the brains of the treated mice, the researchers found changes in the activity of genes that encode portions of the receptor for the neurotransmitter GABA. GABA typically dampens neural activity, and many drugs for treating anxiety disorders target its receptors.
The researchers also found that, if the vagus nerve, a major channel for sensory data from the gut to the brain, was severed, the effect did not occur, providing further evidence that the central nervous system was being affected directly.
How all this works is still a considerable puzzle, but it is another reminder that all of our bodily systems are connected in many different ways.
The MedicalXpress site also has an article on this research.