杏吧原创

Call them the neuron whisperers. Researchers are eavesdropping on conversations going on between brain cells in a dish.

Rather than hearing the chatter, they watch neurons that have been genetically modified so that the electrical impulses moving along their branched tendrils cause sparkles of red light (see video). Filming these cells at up to 100,000 frames a second is allowing researchers to analyse their firing in unprecedented detail.

Until recently, a neuron鈥檚 electrical activity could only be measured with tiny electrodes. As well as being technically difficult, such 鈥減atch clamping鈥� only reveals the voltage at those specific points. The makes the neuron鈥檚 entire surface fluoresce as the impulse passes by. 鈥淣ow we see the whole thing sweep through,鈥� says of Harvard University. 鈥淲e get much more information 鈥� like how fast and where does it start and what happens at a branch.鈥�

The idea is a reverse form of optogenetics 鈥� where neurons are given a gene from bacteria that make a light-sensitive protein, so the cells fire when illuminated. The new approach uses genes that make the neurons do the opposite 鈥� glow when they fire. 鈥淚t鈥檚 pretty cool,鈥� says of University College London. 鈥淚t鈥檚 amazing that you can dispense with electrodes.鈥�

Brain in a dish

Cohen鈥檚 team is using the technique to compare cells from typical brains with those from people with disorders such as motor neuron disease or amyotrophic lateral sclerosis. Rather than taking a brain sample, they remove some of the person鈥檚 skin cells and grow them alongside chemicals that rewind the cells into an embryonic-like state. Another set of chemicals is used to turn these stem cells into neurons. 鈥淵ou can recreate something reminiscent of the person鈥檚 brain in the dish,鈥� says Cohen.

Next, the team will turn their attention to epilepsy. The plan is to test drugs on a personalised 鈥渂rain in a dish鈥� to see which one is most likely to benefit someone.

And it鈥檚 not just neurons that researchers can get up close and personal with. Heart muscle cells also fire electrically as they contract. Cohen鈥檚 biotech venture, , is taking advantage of this to look at how heart cells beat and gauge how different drugs affect their excitability.

In work presented at the in Washington DC this week, his team showed that several drugs that have been linked to heart problems change the firing of heart cells in a dish. 鈥淭his may open up drug screening capabilities,鈥� says one of Cohen鈥檚 collaborators, of the Massachusetts Institute of Technology, who helped found optogenetics.