Optogenetics is an exciting emerging scientific field that is helping provide researchers with new tools to further our understanding of the brain in health and disease. This pioneering method involves using light to control events in populations of living cells, allowing scientists to examine the characteristics of normal and abnormal brain function and also explore novel ways to treat certain neurological disorders.
The technique involves inserting genes into specific groups of brain cells, or neurons, within a region of interest, usually by infecting them with a virus that has been engineered to contain specific DNA sequences. These genes, which are usually sourced from bacteria or jellyfish, then produce a light-sensitive protein which either switches the cells on or off in response to light. This allows scientists to scrutinize how cell types contribute to the function of neural circuits.
Additionally, because this technique can be used in living organisms, such as animal models of Parkinson’s, researchers are gaining new insights into various neurological disorders. And now, new research has hinted that one day, it could be used as a novel way to stop seizures in epileptics.
Earlier work in animals demonstrated that it was possible to use light stimulation to effectively stop seizures in mice that were bred to have different types of seizures. However, it was unclear which brain regions would be most effective at stopping seizures in their tracks when stimulated, which was why neuroscientist Esther Krook-Magnuson and her colleagues recently set out to explore this further.
For their study, which was presented on Monday, November 17th at the 44th annual meeting of the Society for Neuroscience, the researchers used optogenetics to activate cells within the cerebellum, which is a structure known to be involved in controlling body movement. They found that firing these cells during seizures promptly caused them to stop, returning the uncontrolled electrical activity back to normal.
This prompted the researchers to wonder whether inhibiting these same cells would make seizures worse, so they used the same technique again but this time they prevented the cells from firing during seizure. Intriguingly, rather than making the seizures worse, it stopped them. This, says Krook-Magnuson, suggests that it doesn’t matter whether you excite or suppress these cells, so long as you disrupt the existing pattern of firing.
Next, the researchers examined the effects of stimulating a specific type of cell within a structure called the dentate gyrus, which forms part of the hippocampus, a region critical for learning and memory. Some lines of evidence suggested that these cells, called granule cells, may prevent seizure activity in the hippocampus, although no studies had investigated this in live animals before.
Preventing these cells from firing during seizure was found to effectively stop the seizure, whereas stimulating them made the seizures worse. Activating the same cells in healthy mice also caused them to experience seizures. Taken together, this suggests that these granule cells could represent a potential new target for controlling seizures using this method.