Brain cells in the in the abdomen help form the gut-brain connection : NPR

Not all brain cells reside within the brain.

For example, a team at the California Institute of Technology identified two different types of neurons in the abdomen of mice that appear to control different aspects of digestion.

The discovery is reported in a diary naturehelps explain how clusters of neurons in the body play a critical role in the gut-brain connection, a complex two-way communication system between the brain and digestive system.

It also adds to evidence that neurons in the body can perform specialized functions “just like the brain”. Yuki Okastudy author.

“The peripheral nervous system is smart,” says Frank Duca of the University of Arizona, who was not involved in the study.

“There are specific neurons within this system that perform different functions with the help of the brain, and sometimes without brain input,” he says.

Fight or flight gut check

The study focused on a subset of the peripheral nervous system called the sympathetic nervous system, which is activated when the brain senses danger.

“Because you have to fight or flight, your adrenaline increases and the blood sugar levels in your blood become very high,” Oka says.

At the same time, the sympathetic nervous system suppresses less urgent functions, such as digestion and moving food through the intestines.

But how does the system deliver the right messages to each internal organ?

Oka’s team thought the answer might involve specialized neurons that can send different messages to different organs, so they focused on clusters of abdominal neurons called ganglia.

“We looked at one of the large ganglia that controls the function of the lower intestines, including the intestines, spleen, stomach, and liver,” Oka says.

The research team used cutting-edge genetic techniques to characterize the neurons within that cluster. They discovered two different types of cells with distinctly different functions.

“We found that digestion-related functions are controlled by one major cell type, and another type of neuron is involved in intestinal motility,” Oka says.

When the researchers stimulated one type of neuron, the animals’ livers decreased production of enzymes including bile, a digestive fluid that breaks down fat. Stimulating other types of neurons would cause the animal’s intestines to move food more slowly.

Although the study involved mice, Oka says a similar system may exist in humans, who have very similar gastrointestinal tracts.

Special neurons, better medicine?

The study supports a new belief among scientists that specialized neurons in the body play a key role in the gut-brain connection and can influence everything from hunger to mood. It becomes.

Although this study was limited to signals traveling from the brain to the gut, other research suggests that specialized neurons also help send information in other directions, Duca said.

“The gut can send signals to the brain about diet and inflammatory conditions, and the brain can send responses back to the gut about how to react,” says Dr. Duca.

Other internal organs also rely on specialized neurons located outside the brain and spinal cord. For example, the heart contains an internal network of neurons that can regulate electrical and mechanical activity even if the organ is removed from the body.

All of these specialized neurons are potential targets for treating everything from high blood pressure to depression to irritable bowel syndrome, Duca says.

In theory, “future drugs could target only a specific subset of these neurons, activating only one function instead of activating all functions.” Mr. Duca says.

If this approach works, he says, it could lead to more effective drugs with fewer side effects.