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open-connectome-classes / StatConn-Spring-2015-Info

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Glutamate uncaging #200

Open ElanHR opened 9 years ago

ElanHR commented 9 years ago

This term keeps being used and I'm a little unsure of what is meant by it specifically. I'm been taking it to mean "exciting/lighting up (hopefully) the neuron of interest".

yaxigeigei commented 9 years ago

We know how to stimulate neurons electrically - simply shocking them with electrode. But how can we stimulate them using light which would be very convenient when doing imaging? As imichaelnorris said, glutamate is a kind of neurotransmitter naturally used by neurons to excite other neurons. However, we can't pour glutamate directly into the brain because ALL neuron will be activated ALL the time. Uncaging technique utilizes a modified version of glutamate, in this paper it is called Rubi-glutamate, which only becomes effective(excitatory) when activated by focal laser(uncaging, the "cage" is that Rubi-).

ElanHR commented 9 years ago

Ahh got it, that makes sense. Thanks!

indigorose1 commented 9 years ago

Bathing all the neurons with glutamate would also kill them, which is kind of bad... Luckily we have this great way of releasing as much as we want, when we want it, which is a much better option. Basically: save neuron lives, use caged glutamate!

whock commented 9 years ago

Right, so you release a modified form of glutamate that is made inactive by a chemical group bound to it (the "cage") which physically blocks it from binding to any cells or anything. So Glut is there, resting, waiting. And so when the experimenter shines a specific wavelength of light, the link is broken (the "cage" is opened) and glutamate is then free to bind to cells. But the key part is that this happens locally - the laser only excites a small volume of glutamate. So it's a good way to chemically excite individual synapses.

Here's a video of glutamate uncaging at individual synapses. You can clearly see the transient increase in [Glu]. Pretty cool.

https://www.youtube.com/watch?v=dY7qKpi2u_c

akim1 commented 9 years ago

The caption in the video says that the green is GFP-GammaActin. This is just the rearrangement/formation of spines as a result of glutamate stimulation.

yaxigeigei commented 9 years ago

Sorry, I should read the video info first...