Optogenetics helps understand what causes anxiety and depression

Researchers at Ruhr University Bochum (RUB; Germany) coupled nerve cell receptors to light-sensitive retinal pigments to understand how the serotonin neurotransmitter works and, therefore, learn what causes anxiety and depression.

Related: Optogenetics could lead to better understanding of anxiety, depression

Prof. Dr. Olivia Masseck, who led the work, researches the causes of anxiety and depression. For more than 60 years, researchers have been hypothesising that the diseases are caused by, among other factors, changes to the level of serotonin. But understanding how the serotonin system works is quite difficult, says Masseck, who became junior professor for Super-Resolution Fluorescence Microscopy at RUB in April 2016.

The number of receptors for serotonin in the brain amounts to 14, occurring in different cell types. Consequently, determining the functions that different receptors fulfill in the individual cell types is a complicated task. If, however, the proteins are coupled to light-sensitive pigments, they can be switched on and off with light of a specific color at high spatial and temporal precision. Masseck used this method, known as optogenetics, to characterize, for example, the properties of different light-sensitive proteins and identified the ones that are best suited as optogenetic tools. She has analyzed several light-sensitive varieties of the serotonin receptors 5-HT1A and 5-HT2C in great detail. Together with her collaborators, she has demonstrated in several studies that both receptors can control the anxiety behavior of mice.

To investigate the serotonin system more closely, Masseck and her research team is currently developing a sensor that is going to indicate the neurotransmitter in real time. One potential approach involves the integration of a modified form of a green fluorescent protein into a serotonin receptor.

This protein produces green light only if it is embedded in a specific spatial structure. If a serotonin molecule binds to a receptor, the receptor changes its three-dimensional conformation. The objective is to integrate the fluorescent protein in the receptor so that its spatial structure changes together with that of the receptor when it binds a serotonin molecule, in such a way that the protein begins to glow.

Full details of the work appear in Rubin Science Magazine; for more information, please visit http://rubin.rub.de/en/controlling-nerve-cells-light.