Neuron Clusters Control Grooming in Mice

24/11/2021

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An international study on mice with participation from RWTH researchers show that specific brain areas can be activated by light pulses.

 

About 130 years ago, the Spanish anatomist Carlos Calleja y Borja-Tarrius described islands of neurons deep in the brain. For a long time, the function of these cells were only poorly understood. Now, an international team of researchers from RWTH, the University of Florida, and the University of Pennsylvania succeeded in deciphering the function of this special brain structure for the first time. According to the study, the so-called Calleja Islands act as a command center for grooming behavior.

First, the exact location and anatomy of the Calleja Islands in mice was investigated in the lab. In their experiment, the researchers changed the optical properties of the brain tissue and thus made it transparent. Using a special microscope, they were able to look deep into the brain tissue, in which only the nerve cells of these islands were visible in red fluorescent light. The research led to an astonishing discovery: The supposed islands actually form a large coherent structure of nerve cells that more closely resembles deer antlers or roots. Using modern genetic methods, the researchers introduced a light-sensitive protein was then introduced into the neurons in order to control the activity of these cells using laser light pulses.

A behavioral experiment shows that the mouse starts grooming as soon as the nerve cells are activated. In turn, the animals' natural grooming behavior can be stopped experimentally with the help of another light-controlled protein that briefly paralyzes the nerve cells. "We use modern tissue clearing and optogenetics techniques for this," explains Dr. Marc Spehr, who is Lichtenberg Professor at the Institute of Biology II and leading the studies at RWTH. According to Spehr, this proves that the Calleja Islands are a control center for grooming behavior. "We assume that our findings can make a significant contribution to a mechanistic understanding of psychiatric diseases," says Spehr.

The activities of the RTG 2416 and IRTG 2150 research training groups and funding from the RWTH’s Exploratory Research Space (ERS) were instrumental in the success of this research, among other factors. “The close interdisciplinary collaboration with the Institute of Imaging and Computer Vision was essential as well,” emphasizes the biologist.

The research results were recently published under the title of Ventral Striatal Islands of Calleja Neurons Control Grooming in Mice in the journal Nature Neuroscience.