Beeld: KU Leuven
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Brain cells communicate not only by firing signals to each other through synapses. They also inform each other via small proteins called neuropeptides. Little is still known about this alternative brain network’s precise operation and function. But that may soon change now that neurobiologists, including those from the Leuven Brain Institute, have already mapped the network in the roundworm C. elegans. The university writes this in a press release.

  • Neurobiologists at KU Leuven have painted a detailed picture of brain networks.
  • This breakthrough offers deep insight into the complex interactions and communication within the brain.

Brain and nerve cells interact with each other using chemical and electrical signals. Well-known is synaptic signaling. In this process, neurons provide electrical stimuli to each other, using neurotransmitters. However, this signal transmission occurs only between physically connected neurons via synapses.

Firing signals

But neurons possess another means of communication. While firing signals along synapses, they can simultaneously release small proteins called neuropeptides. The free molecules then spread through brain tissue to other neurons, which may be even relatively distant. Depending on their type, the neuropeptides may or may not be detected by the neurons – for that, the neurons must have the corresponding receptor molecules. A well-known example of a neuropeptide is oxytocin, which plays an important role in social bonding and is sometimes called the cuddle hormone.

Wireless network

One advantage of communication via neuropeptides is that a sender neuron can activate other neurons for long periods of time. This differs from synaptic signal transmission, which operates on a much shorter time scale. Another difference is that sender and receiver neurons do not have to be physically connected. Thus, the so-called neuropeptide brain network is “wireless.

Neurobiologists at KU Leuven, in collaboration with British colleagues, have now mapped this brain network for the first time. They did so in the roundworm C. elegans, a popular model organism in neurobiology. The compilation of the first overview map of the neuropeptide network is a milestone, similar to the first mapping of the synaptic brain network nearly forty years ago – also in C. elegans.

Of course, both the synaptic and neuropeptide networks are very important for the proper functioning of the brain. But where the former is easily visible anatomically (the synapses show up in slices of brain material under the microscope, for example), this is not the case at all with the latter. “Neuropeptide interactions are not anatomically visible, and so for that, you need special research techniques,” said Isabel Beets, professor of neurobiology at the Leuven Brain Institute. “Partly because of this, the brain network could only now be mapped.” Beets, along with Liliane Schoofs and William Schafer, led the Leuven component of the research collaboration.

Understanding the neuropeptide network is crucial for further progress in brain research. Beets: “Efforts are currently being made in various animal species to map the synaptic network in the brain. Several large research projects focus on this. But without the neuropeptide network, the brain puzzle is not complete.” After all, this brain network is completely self-contained (something that has actually only recently been known). It enables communication separate from the synaptic network.

A lot of potential

Research into the neuropeptide network also has great potential in neurology. After all, numerous disorders can be traced back to specific neuropeptides and their corresponding receptors. GLP-1, for example, is a peptide whose production in the pancreas falters in diabetics. But the protein is also produced in the brain, as a signaling agent of the neuropeptide network. Other neuropeptides are involved in brain processes linked to addiction and obesity. And neuropeptide receptors are already being targeted directly, as in new migraine medication.

The compilation of a first overview map of the neuropeptide network is now giving research into it a big boost. The map shows all interactions between the 302 neurons of C. elegans, accounting for more than thirty thousand interactions. Researchers can consult the map, which indicates for each neuropeptide which neurons it connects (wirelessly), to further study the brain network. The research is detailed in two articles published in the journals Cell Reports and Neuron.