Taking doses of strong antibiotics may eliminate bacteria in the gut, but according to a new study, these drugs may produce adverse effects on the part of the brain that handles memory.
The same research has also identified white blood cells that appear to serve as a link between the immune system, the gut and the brain.
Researcher Susanne Asu Wolf and her colleagues at the Max-Delbrueck-Center for Molecular Medicine in Germany have found that long-term use of antibiotic treatment could negatively impact certain functions of the brain.
However, the scientists said this effect can be balanced out through exercise and taking probiotics. They also stressed that antibiotics should be considered as a viable treatment option.
For their study, Wolf and her team examined how mice would react to being given antibiotics in order to treat their intestinal microbes. The drugs were able to get rid of the health gut bacteria in the mice but had also caused the animals to perform poorly during memory tests. The treatment also affected neurogenesis, or the production of new brain cells, in the hippocampus of the creatures.
The researchers also discovered that the mice also experienced low levels of white blood cells, particularly those known as Ly6Chi monocytes, typically found in the brain, bone marrow and blood of an individual. The team decided to find out whether these Ly6Chi monocytes are the ones responsible for changes in memory and neurogenesis.
Wolf and her team conducted another experiment where they compared the health of untreated mice with those of mice that had healthy levels of gut bacteria but with poor levels of Ly6Chi, which could be caused by genetics or antibiotic treatment specifically designed to attack Ly6Chi cells.
The researchers discovered that the mice that had low levels of Ly6Chi experienced the same problems with their neurogenesis and memory as those featured in the previous experiment that had lost their gut bacteria.
Interestingly, the team also found that if they were to replace the Ly6Chi levels of mice treated with antibiotics, then the creatures' neurogenesis and memory would improve.
The negative impact of using antibiotics has been shown to be reversible. Mice that were given probiotics or made to exercise on a wheel after having been given antibiotic treatment were able to regain their neurogenesis and memory.
One downside the researchers found, however, was that even though giving the mice probiotics was able to restore their proper memory function, fecal transplants to restore their healthy gut bacteria proved to be ineffective.
While the transplants were able to bring back lost gut bacteria, it did not improve neurogenesis in the mice.
Wolf and her colleagues are now planning to conduct experiments to determine whether probiotic treatments could benefit people suffering from psychiatric and neurodegenerative disorders.
The findings of the Max-Delbrueck-Center for Molecular Medicine study are featured in the journal Cell Reports.