Optogenetics Flashcards
Optogenetics
a neuromodulation technique employed in neuroscience that uses a combination of techniques from optics and genetics to control and monitor the activities of individual neurons in living tissue - even within freely-moving animals - and to precisely measure the effects of those manipulations in real time. Key reagents: light sensitive proteins. Spatially-precise neuronal control is achieved using optogenetic actuators like channelrhodopsin, halorhodopsin, and archaerhodopsin
Channelrhodopsin
channel that responds to light. Absorbs blue light. Nonspecific cation channels, conducting H+, Na+, K+, and Ca2+ ions. Activation. After exposure to blue light, the channel immediately depolarizes the neuron and then generates APs
Halorhodopsin
light-gated ion channel, specific for Cl ions.used to achieve inhibition (hyperpolarization**) of action potentials in mammalian neuron systems
What Are Optogenetic Actuators?
Light-sensitive proteins which are key reagents used in optogenetics (Ec. ChR2, NpHR, and archaerhodopsin
How Do Optogenetic Actuators Work?
They absorb light and cause changes in neuronal signals/spikes, such as ionic currents.
What it means: “Optogenetic Stimulation of Neural Activity”
Ex. label active neurons during contextual fear conditioning by driving expression of ChR2 to DG neurons expressing the c-fos promoter.
Mice placed in novel context A and active neurons were labeled with ChR2
This population of neurons was then optically activated during fear conditioning in context B
When placed back in A, they showed enhanced freezing even though they were never shocked in context A, in effect creating a false memory representation.
C-fos is a transcription factor…
What it means: “Optogenetic Inhibition of Neuronal Activity
enhancing halorhodopsin chloride channel which acts as an optogenetic inhibitor will result in impaired retrieval of remote memory
How Are Neurons Engineered to Express Opsins
Expression of ChR2 can be restricted to specific types of neurons by injection of viral vectors encoding the opsin to specific brain areas or by incorporating the opsin under the control of a specific promoter activated in the same types of neurons. (This virus, when injected into an area of the brain, is able to recombine its DNA with the DNA of the host cells. Once recombined, all of the cell dynamics and machinery necessary to express the ion channel gene is available, and the cell will begin expressing the channels on its cell membrane.)Using genetically and/or anatomical approaches, many studies restrict expression of the opsin to specific brain regions or cell types of interest.
How Are Neurons Illuminated during experiments involving optogenetic regulation?
Lasers shine light on desired brain regions (that have been injected with viral vector/opsin) using an implant/ optic fiber and then an amplifier/computer helps visualize
