lecture 14- fixing faulty circuits Flashcards
Why are small organic compounds sometimes used instead of channelrhodopsin in visual circuits
non invasive
broader wavelength range
what feature of small organic molecules allows them to respond to light
switch between cis/trans conformation
trans -> Cis at 380nM
cis ->trans at 500nM
which kind of ligands can be added to small organic compounds and why
GABA receptors
ACh receptors
potassium channels
glutamate receptors
allows them to be conditionally active
what is retinitis pigmentosa
decreased field of view due to photoreceptors disappearing
how can we solve retinitis pigmentosa
using an artificial retina
during disease treatment, when would we need to activate the visual cortex
when the optic nerve hasnt developed
why do we need too activate the visual pathway as anatomically early as possible
if you stimulate RGCs with a simple stimulus they are useless
How can we activate faulty photoreceptors in RP
electrical stimulation
light stimulation(channelrhopdopsin and halorhodopsin)
what is the issue with electrical stimulation for activating faulty PRs
it stimulates RGCs, not photoreceptors or bipolar
why is light stimulation better than electrical stimulation
it can stimulate deeper layers
how is halorhodopsin used to stimulate photoreceptors in RP mutation
it is expressed in the remenants of photoreceptors to try and mimick hyperpolerisation
what are 3 bits of evidence that halorhodopsin can stimulate degraded photoreceptors
1- ganglion cells still have their ON / OFF nature
2- centre surround organisation of RGCs is still intact
3- direction selectivity is intact
How does epilepsy arise
from an imbalance between excitatory glutamate activity and inhibitory GABA activity
what are the 2 ways to control epilepsy using light
implant channelrhodopsin/ halorhodopsin into cells with a virus into neurons
halo for excitatory cells to block glutamate release
channel for inhib cells to activate GABA release
what are the issues with using light to target and prevent epilepsy
only tested in mice
problems with glial cells/astrocytes can also cause epilepsy even when the neurons are fine
need to make sure the light implants dont cause infection
hard to detect a seizure before it actually starts
