For yrs, neuroscientists have been trying to develop tools that would allow them to clearly view the brains circuitry in action - from the 1st moment a neuron fires to the resulting behavior. Researchers have now developed a #tool that provides a new way of #mapping #neural #networks in a living organism. The tool detects and serves as a marker of action potentials. >>The researchers began by optimizing #Archaerhodopsin (Arch), a light-sensitive protein from bacteria. In nature, opsins like Arch detect sunlight and initiate the microbes #movement toward the light so that they can begin photosynthesis. But you can also exploit the light-responsive qualities of #opsins for a #optogenetics (where organisms neurons are genetically modified to express these microbial opsins). Then, by simply shining a light on the modified neurons, the researchers can control the #activity of the cells as well as their associated #behaviors in the organism. #MOA: ~When the modified neurons are exposed to #green light, #Arch acts as an #inhibitor, thus associated behaviors, by preventing nn firing. ~ when exposed to #red light, the protein acts as a #voltage #sensor, responding to changes in membrane voltages by producing a flash of light in the presence of an #action #potential (but light was too dim) ...SO they use directed evolution to make the protein brighter. ...eventually came up with mutant #Archer1, ...was not only bright and sensitive enough to mark action potentials in mammalian neurons in real time, it could also be used to identify which neurons were synaptically connected -- and communicating with one another -- in a circuit. >> Although the proteins fluorescence can be seen through the nearly transparent tissues of the nematode worm, opaque organs such as the mammalian brain are still a challenge. More work, she says, will need to be done before Archer1 could be used to detect voltage changes in the neurons of living, behaving mammals. >> Gradinaru next hopes to use tools like Archer1 to better understand the complex neuronal networks of mammals, using #microbial #opsins as #sensing and #actuating tools in optogenetically modified rodents. caltech.edu/content/sensing-neuronal-activity-light
Posted on: Fri, 19 Sep 2014 17:01:55 +0000
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