11 - Fixing faulty neural circuits Flashcards
What is channelrhodopsin ChR?
A non-selective ion channel
What happens when ChR opens?
The membrane depolarises.
How is channelrhodopsin activated?
By light, specifically blue light.
What did using channelrhodopsin in mouse brains tell us?
- That expressing ChR in certain neurons in vivo you can modify behaviour and the activity of different neurons.
- It can also be used to fix defected neurons.
What is Halorhodopsin?
Another type of ion channel that is only selective to Chloride ions.
How is Halorhodopsin activated?
By red light.
What happens when halorhodopsin is stimulated?
The neuron hyperpolarises below the threshold.
What do double bonds do in small organic compounds of ChR?
They create the possibility for the coumpound to have 2 compositions. Cis and Trans.
What is transconformation?
When both parts of the molecule are on opposte sides of the double bond.
What is cisconformation?
When both parts of the molecule are on the same side of the double bond.
What happens of the compound/molecule when light is shined on it?
It turns from trans to cis conformation.
What happens if another light with a different wavelength is shined on the molecule?
The proces reverses and it turns from cis conformation to trans confrmation.
What does shining a light on a molecule help us do?
Regulate the distance fron the active part to the protein of interest.
What can adding a GABA receptor ligand or glutamate receptor ligand help with?
Lets us activate the receptors using light rather than than GABA molecule itself.
What is Retinitis Pigmentosa?
One of the most common caues of blindness, it decreases the field of view as it progresses.
What causes retinitis pigmentosa?
- Mutations that cause a decrease in the number of photoreceptors.
- Bipolar cells don’t receive input from the photoreceptor so they start to degenerate.
What are some ways to fix retinitis pigmentosa?
- Genetically modify photoreceptors to stop they from dying.
- Stimulate the visual neurons to help restore vision, done by electrodes or optogenetics. —> done by activating the retina/visual system through an electorde in the V1 cortex of the brain.
What are the 2 major classes of ganglion cells?
Parvocellular cells and Magnocellular cells.
What are some characteristics of parvocellular cells?
- They have centre surround organisation.
- They have a smaller receptive field.
What are some characteristics of magnocellular cells?
- They also have centre surround
organisation. - They have a larger receptive field.
- They can respond to different colours of
light.
How is direction selectivity evident in the retina?
It responds to movements in some directions but not others.
To solve this light is used to stimulate deeper layers.
What are brain circuits composed of?
Excitatory and inhibitory neurons.
What do excitatory neurons release?
Glutamate.
What do inhibitory neurons release?
GABA.
How does epilepsy arise?
From an imbalance between excitation and inhibition
What can be done to control seizures?
- Using halorhodpsin in excitatory cells
- Using channel rhodopsin in inhibitory cells.
- Inject a virus that expresses optogenetic tools.
