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Optogenetics is the controlling of cell action using a combination of genetic and optical techniques. This method began with the discovery of biochemicals that produce cellular responses when exposed to light. By isolating the genes that code for these proteins, scientists use them to stimulate light responses in other living cells. The knowledge gained from optogenetics provides researchers with greater insight into various disease processes.
In the 1970s, scientists discovered that certain organisms produce proteins that control the electrical charges which normally pass across cellular membranes. These proteins caused intertaction between cells when exposed to certain wavelengths of light. These proteins, commonly referred to as G-proteins, are encoded by a group of genes known as opsins. During this time, researchers found that bacteriorhodopsins respond to green light. Further research discovered other members of the opsin family, including channelrhodopsin and halorhodopsin.
During the decade 2000 to 2010, neuroscientists found that it is possible to extract opsin genes and insert them into other living cells, which then acquire the same photosensitivity. One of the methods initially used involved removing opsin genes, combining them with a benign virus, and inserting them into live neurons in a petri dish. When the injected cells were exposed to pulses of green light, the neurons responded by opening ion channels. With the channels open, the cells received an influx of ions which caused an electrical current to flow, initiating communication with another neuron. Scientists discovered that other G-proteins respond to different light colors, inhibiting or enhancing calcium ion channels and epinephrine release.
Research eventually progressed from applying optogenetics to a small group of live cells to using live mammal subjects. By introducing the opsin genes into the brains of mice, the cells began producing the G-proteins. With these G-proteins and fiber optics, scientists were able to control the rate of neuron firing. They also developed a method of converting a small optic fiber into an electrode to provide an electrical readout of cellular activity. This brain-computer interfacing allows researchers to evaluate and regulate specific groups of cells anywhere in the brain.
By combining magnetic resonance imaging (MRI) and optogenetics, researchers are able to map neural activities and pathways within the brain. By exploring the intricacies of neurological function, physicians gain a better understanding of what constitutes normal and abnormal brain activity. Unlike medications and electrotherapy, optogenetics allows regulation of specific cells and pathways. The knowledge and technology obtained from optogenetics also allows control of the function of cardiac cells, lymphocytes, and insulin secreting pancreatic cells.
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