Neuron-astrocyte networks, depression and addictions

Research reveals the importance of a class of brain cells, astrocytes, for the functioning of a region of the brain related to moods.

The study has been carried out by a team that includes Marta Navarrete, a researcher at the Higher Council for Scientific Research (CSIC) at the Cajal Institute, both institutions in Spain.

The results of the study show that astrocytes, the most numerous non-neuronal cells in the brain, are decisive in reward systems. The findings underscore the importance of studying neuron-astrocyte networks in the nucleus accumbens, a brain region that triggers reward-oriented behaviors, as therapeutic targets in pathologies such as addiction or depression, related to changes in reward circuits of the brain.

“Despite the fact that the nucleus accumbens is made up of both neurons and astrocytes, until now it had been believed that neurons were the only ones responsible for its functions”, explains Marta Navarrete. “We have discovered that the astrocytes of the nucleus accumbens respond differently to signals from different regions involved in tasks such as memory and learning (hippocampus), emotions (amygdala), or decision-making (prefrontal cortex) and that, in addition, are organized in specific networks”, explains the researcher. The work shows that astrocytes are capable of integrating information signals in a non-linear way, which reveals the neuron-astrocyte network as a key to the integration properties of the nucleus accumbens.

The researcher points out that the results highlight the need to study functional maps and not only neuronal ones, since they have shown that astrocytes play an active role in synaptic function and in the processing of neuronal information through the exchange of signals with neurons. “If we advance in the study of the functionalities of accumbens, we will not only better understand diseases related to mood, but we will also be able to find effective therapeutic targets,” says Navarrete.

Astrocyte-neuron networks in the nucleus accumbens. (Image: Marta Navarrete (CSIC))

A method for mapping neuron-astrocyte networks

The researchers have implemented a new study tool (CaMPARIGFAP) that has allowed them to analyze specific neuron-astrocyte circuits for the first time. “It is a calcium sensor with which we have been able to develop a spatial analysis of the activity of astrocytes on a large scale. It is a very versatile method for analyzing ex vivo and in vivo fixed tissue”, explains Irene Serra, CSIC researcher at the Cajal Institute and first author of the study.

The study has combined the use of this new tool with experimental techniques such as optogenetics to stimulate specific circuits with light and electrophysiology to stimulate neuronal activity. “This methodology has allowed us to advance in the study of neuron-astrocyte networks and can be very useful to continue on the path of understanding the functioning of reward circuits”, says the researcher.

The study is titled “Ca2+-modulated photoactivatable imaging reveals neuron-astrocyte glutamatergic circuitries within the nucleus accumbens”. And it has been published in the academic journal Nature Communications. (Source: Esther M. García Pastor/ CSIC)