Active Transmembrane Water Cycling For Neuronal Activity Detection

Neurons absorb and release water when they relay messages throughout the brain, according to a study by researchers at the National Institutes of Health and other institutions. Tracking this water movement with imaging technology may one day provide valuable information on normal brain activity, as well as how injury or disease affect brain function.

Current functional magnetic resonance imaging (fMRI) technologies measure neuronal activity indirectly by tracking changes in blood flow and blood oxygen levels.

Neurons communicate with each other by a process known as firing. In this process, they emit a slight electrical charge as an enzyme moves positively charged molecules — potassium and sodium ions — through the cell membrane.

In the current study, when researchers stimulated cell cultures of rat neurons to fire, they found that the exchanges of potassium and sodium ions was accompanied by an increase in the number of water molecules moving into and out of the cell.

Neuronal Firing

The researchers, led by Peter Basser, Ph.D., noted that their method works only in cultures of neurons and additional studies are necessary to advance the technology so that it can be used to monitor neuronal firing in living organisms.

Basser is Senior Investigator, Section on Quantitative Imaging and Tissue Science, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health.

Funding for the work came from the Intramural Research Program (IRP) of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institute of Mental Health, Fundamental Research Funds for Central Universitie, Zhejiang University, and the OHSU Advanced Imaging Research Center.

Bai R, Springer CS Jr., Plenz D, Basser PJ
Brain active transmembrane water cycling measured by MR is associated with neuronal activity
Magn Reson Med. 2018;00:1–16. https://doi.org/10.1002/mrm.27473

Image: Collin Edington and Iris Lee, Koch Institute MIT. CC BY-NC-ND. This image shows a ‘brain organoid’ composed of neural progenitor cells that differentiate into different neuronal subtypes when cultured on a coat of synthetic PEG (polyethylene glycol) hydrogel.