Researchers have demonstrated the existence of a neural connection between the gut and the brain stem. Until now, only a slower hormonal communication had been described to explain hunger control. Our brain receives information from all five senses, vision, hearing, touch, taste, and smell, which are quickly transmitted by sensory networks that carry electrical messages.
The intestines also send signals to the brain, but most of these messages are related to the metabolism. To achieve that, the human gut uses hormonal communication by releasing molecules into the bloodstream. In the intestinal epithelium, there are cells called “enteroendocrines” that act as sensory sensors, and “reads” the nutrients present there. The nutrients in the intestines stimulate the release of hormones, to inform the brain.
Until now, it was thought that these sensory cells only act through the slow pathway of hormones such as cholecystokinin. The researchers suspected the existence of a faster mechanism because the sensory cells present in the human gut have similarities with those of the tongue and nose.
The human gut communicates directly with the brain stem
In this new research published in Science, researchers at the Duke University wanted to better understand the circuit between the human gut and the brain. To do this, they used a rabies virus marked with a green fluorescence that they injected into the stomach of mice to follow its path from the intestine to the brain. The researchers observed that the virus passed through the vagal nerve to reach the brain stem. Additionally, the researchers showed that enteroendocrine cells have presynaptic proteins.
“Scientists talk about signaling in terms of minutes and hours. We are talking about a few seconds here,” Diego Bohorquez, one of the authors of this work, said in a Duke University statement. However, this has implications for the development of new obesity therapies because many of the appetite suppressing molecules that have been studied target slow-acting hormones, not fast-acting synapses.
In conclusion, the researcher found a connection between the human gut and brain stem, changing the way scientists view the communication between intestines and brain.