L12 - correction of faulty neural circuits Flashcards

1
Q

what is channelrhodopsin

A

non-selective channel, stimulated with light, causing channel to open

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2
Q

what light is channel rhodopsin stimulated by

A

blue light 460nm

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3
Q

what happens if switch of the light

A

closes faster when stimulated with 360nm

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4
Q

what happens when switch on the light - channelrhodopsin

A

neuron is depolarised and sufficient to trigger a strike

the spike occurs everytime the neuron is stimulated

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5
Q

halorhodopsin

A

stimulated by yellow light 570nm. causes hyperpolarisation of the membrane

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6
Q

what is the problem with using rhodopsin channels in humans

A

don’t have the technologies to do so - express them in viruses which may not be safe

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7
Q

what can be used instead of channelrhodopsin

A

2 small molecules - optical isomers of each other

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8
Q

important parts of the small molecules

A

maleimide - binds to a specific channel
azobenzene - functions to change depending on stimulation of light
quaternary ammonium - serves as a block of the channel

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9
Q

at what light does the trans isomer turn into the cis isomer

A

380nm

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10
Q

at what light does the cis isomer turn back into the trans isomer

A

500nm

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11
Q

what does the trans isomer do?

A

block the channel - when turned into cis isomer, the block is removed

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12
Q

how does the small molecule work ?

A

enters the TRPV1 channel and acts on the channels from the inside of the cell

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13
Q

why is it important that it works inside the cell

A

stays inside the cell longer

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14
Q

what is the GABA receptor important for

A

regulating the overall excitability of the NS

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15
Q

what causes epileptic seizures

A

overexitability of neurons in the brain

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16
Q

what wavelength can activate the GABA receptors

A

380nm light

17
Q

what occurs when the GABA receptors are activated

A

hyper polarise the cells and remove hyperexcitabiltiy of the neurons

18
Q

what is retinitis pigmentosa

A

a disease in which the field of view becomes smaller and smaller until the patient becomes blind

19
Q

what causes retinitis pigmentosa

A

retinal degeneration which starts with the dying of the photoreceptors - rods and cones
as it progresses other cells in the retina become degernated (bipolar and ganglion cells)

20
Q

what is the treatment for retinitis pigmentosa

A

artificial retina or gene therapy

can use electrodes or tools to stimulate the visual system

21
Q

problems with using electrodes to stimulate neurons

A

chronic implantation of electrodes in the brain/retina will cause degeneration of the tissue around the electrodes as electrodes may hear up and kill surrounding neurons

22
Q

what are the 2 areas needed to stimulate to cure blindness

A

retina - for retinitis pigmentosa

visual cortex - when optic nerve didn’t develop/destroyed

23
Q

how are the retina and visual cortex stimulated

A

either by electric stimulation of channelrhodopsin and halorhodopsin

24
Q

problems with artificial stimulation of retina

A

stimulates ganglion cells but not photoreceptors or bipolar cells

25
what are the 2 main classes of ganglion cells
parvocellular and magnocellualr
26
size of parvocellular dendritic tree
small
27
size of magnocellular dendritic tree
large
28
what type of receptive fields to ganglion cells have
centre surround organisation
29
what is a centre surround organisation
if stimulate ganglion cell in centre of the receptive field will have increase / decrease in spiking rate. if stimulate outside of receptive field will get opposite result in spiking rate
30
what happens when switch of the light stimulating a ganglion cell
decrease in spiking rate
31
what occurs when stimulate halorhodopsin in photoreceptors
get hyperpolarisation - leads to decrease in release of glutamate from the synapses
32
what does intact centre surround organisation of RGCs in retinitis pigmentosa show
shows that can restore the basic properties of the cells
33
what is intact during retinitis pigmentosa
diversity center surround organisation direction selectivity
34
what are the 2 ways to control seizures
- use halorhodopsin expressed in excitatory cells - hyperpolarise the excitatory cell use channelrhodpsin - depolarise inhibitory cells - so when stimulate the cell with blue light they release more GABA
35
what tools are used to inject a virus to treat seizures
ontogenetic tools
36
questions needed to ask to treat
where to express optogenetic tools where is the seizure of the origin excitatory or inhibitory neurons