An artificial gut that mimics bacterial interaction with intestinal cells is shedding light on how events in the digestive tract affect the brain.

The HuMiX model, about the size of a beer mat, houses growing cultures of gut cells and bacteria which are exposed to nutrients flowing from a supply chamber.

Different bugs can be tested to see how the human "microbiome" - the community of all the micro-organisms living in the human body - impact on health via the gut.

Scientists have already shown how one strain of bacteria, Lactobacillus rhamnosus, causes gut cells to generate a nervous system messenger chemical.

Dr Pranjul Shah, from the University of Luxembourg, one of the inventors of the device, said: "We determined that production of a messenger of the nervous system, specifically the neurotransmitter gamma-aminobutyric acid, or GABA, is stimulated in intestinal cells, indicating a mechanism by which the intestine may be communicating with the brain."

One function of GABA is to calm down over-excited neurons, which may have the effect of controlling fear and anxiety. Certain drugs, such as Valium, work in a similar way.

Gut bacteria may also be involved in inflammatory processes that play a role in neurodegenerative diseases such as Parkinson's.

"In HuMiX we can introduce distinct bacterial species, or whole communities, into the artificial gut model to see whether these organisms trigger or slow down inflammation, or even introduce immune cells and neurons together with bacteria," said lead researcher Professor Paul Wilmes, also from the University of Luxembourg.

He added: "Insights in to the function of the human microbiome are a key to our understanding of human health and disease."

A study looking at the effectiveness of HuMiX appears in the journal Nature Communications.

Several pharmaceutical companies are understood to be showing interest in the device, which opens up new doors for drug development.

HuMiX could be used to test new medicines in place of germ-free laboratory mice, which cannot accurately simulate conditions in the human gut. Only a third of new drugs tested on mice end up being successful in clinical trials.