The sleep neuron in wireworms is also an arresting neuron

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Wagner Steuer Costa in the team of Alexander Gottschalk, professor of molecular biology and neurobiochemistry, discovered the neuron sleep RIS a few years ago by chance, simultaneously to other groups. To understand the function of individual neurons in the plexus, researchers use genetic engineering to produce light-sensitive proteins. With these "photocwitches", neurons can be turned on or off in the transparent worm using light radiation of a certain wavelength. "When we saw that the worm was frozen when this neuron had been stimulated by light, we were quite surprised.This was the beginning of a study that lasted for several years," remembers Gottschalk.

The RIS neuron puts C. elegans to sleep when it is active for a few minutes or hours – for example after the loss of the cuticle (a form of secreted skin) that is a process in the development of the animal. He also sleeps to recover from cellular stress. On the other hand, the neuron serves to stop the worm during locomotion, for example, if it wants to change direction or avoid a danger. The neuron then slows the movement of the animal so that it has time to decide if it wishes to continue crawling. In this case, the neuron is only active for a few seconds. "Such stop neurons have only recently been discovered – it's the first of its kind in a worm," says Gottschalk.

Interestingly, the axon of the RIS neuron is apparently branched, the two branches having different functions, so that the RIS slows down not only the movements, but can also introduce a backward motion. Gottschalk and colleagues, Professor Ernst Stelzer of Goethe University, Professor Sabine Fischer of the University of Würzburg, researchers from Vanderbilt American University in Nashville and KU Leuven in the current issue of Nature Communications.