Wednesday, June 13, 2012

Bacteria in the gut instrumental for happy feelings

Happiness is a feeling that is generated in the brain by several molecular signals. Especially important is the neurotransmitter serotonin, that functions as the main component of the 'happy brain'. Lack of serotonin is associated with depression, and treatment involves letting serotonin do its job for a longer period of time. Therefore, it is important for our well-being that we have serotonin flowing through our brains, even though there are several other components that play a role in happy or unhappy feelings. Scientists from the University College in Cork have discovered that the levels of serotonin are regulated by something quite unexpected: bacteria.

During the development phase, in which the body forms and matures, several bacterial species find their way into the gut. There, they find themselves a permanent home, cooperating with our gut cells to digest food. We cannot function without these bacteria, and there are actually more of them than we have cells in our body. Cork scientists discovered that they have an additional function: regulating serotonin levels. They discovered that by using a so-called 'germ free' mouse model.

Mice without gut bacteria in early life were found to have permanent changes in their neural circuits. Among those, a lack of serotonin activity was found to be the most pronounced. As this neurotransmitter is involved with feelings of happiness, it appears that bacteria actually regulate our feelings. Perhaps even more peculiar is that when the scientists restored the bacterial balance in the gut, the neurological connections could not be restored. That means that the bacterial activity in early life is instrumental in the development of the brain, but especially for the circuits that function with serotonin.

The Cork scientists have shown that gut feeling actually translates into good feeling. By showing that the gut and the central nervous system are connected, something that was already expected from earlier research, we may be able to modify brain circuits by aiming at bacteria. Despite these interesting findings, more research is required to unravel the underlying mechanism behind this connection. By doing that, we may be able to develop probiotics that function as a treatment for certain neurological disorders.

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