By Olivia Solon, Wired UK

In a scientific first that could help us better understand how signals travel in the brain, a researcher of natural sciences at Harvard has created neurons that light up as they fire.

[partner id="wireduk" align="right"]Despite the fact that almost every science animation ever created has shown neurons to light up, in reality there is no obvious visual cue to indicate their electrical activity. The genetically altered neurons use a gene from a Dead Sea microorganism that produces a protein that fluoresces when exposed to the electrical signal in a neuron, allowing researchers to visually trace how signals are transmitted through cells.

The research was led by Adam Cohen, Associate Professor of Natural Sciences, and was published in Nature Methods.

In a Harvard Gazette story, Cohen said of the research: "It's very exciting. In terms of basic biology, there are a number of things we can now do which we've never been able to do. We can see how these signals spread through the neuronal network. We can study the speed at which the signal spreads, and if it changes as the cells undergo changes. We may someday even be able to study how these signals move in living animals."

In order to create the snazzy neurons, the team cultured brain cells in the lab and then infected them with a genetically altered virus that contained the protein-producing gene. Once the cells were infected, they started to manufacture the protein themselves, which allowed them to light up.

A neuron has an active membrane around the whole cell and normally the inside of the cell is negatively-charged relative to the outside. However, when the neuron fires, the voltage reverses briefly (for around 1/1,000th of a second). This brief spike in voltage travels down the neuron and then activates other neurons downstream. The genetically-altered protein sits in the membrane of the neurons and light up as the pulse passes through them.

The research could aid our understanding of how electrical signals move through the brain and around the body, Cohen said.

He explained to the Harvard Gazette: "Before, the best way to make a measurement of the electrical activity in a cell was to stick a little electrode into it and record the results on a volt meter. The issue, however, was that you were only measuring the voltage at one point, you weren't seeing a spatial map of how signals propagate. Now, we will be able to study how the signal spreads, whether it moves through all neurons at the same speed, and even how signals change if the cells are undergoing something akin to learning."

Using electrodes can also kill the cells relatively quickly, so it's hard to perform longer studies. The new technique could allow researchers to study cells for much longer.

The research could also prove useful for the development of drugs, many of which target ion channels – proteins that play an important role in governing the activity of the heart and brain. Currently, if researchers want to test a compound designed to activate or deactivate an ion channel, they have to test it with an electrode, then add the drug and see what happens - a process that takes a few hours for every data point. The ability to see how neurons are firing could radically speed up the testing process.

You can read the full study, titled Optical recording of action potentials in mammalian neurons using a microbial rhodopsin here.

Image: Nature Methods/Joel Kralj, Adam Douglass, Daniel Hochbaum, Dougal Maclaurin and Adam Cohen

Source: Wired.co.uk*

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