Optogenetics

Question 1

Dupret (2016)

Answer 1

C-fos archaerhodopsin optogenetic approach to silence hippocampal neurons that are active in particular environment, unmasking alternative map. When procedure applied in a cocaine-paired environment neutralised long-lasting drug/place preference , showing recoding of a spatial memory engram alleviating associated maladaptive behaviour.

Question 2

Jennings (2013)

Answer 2

vBNST neurons project to VTA, shown through antidromic photostimulation assays. In vivo stimulation of glut projections produces aversive and anxiogenic behavioural phenotypes, activating GABA produced rewarding and anxiolytic phenotypes.

Question 3

Kash (2016)

Answer 3

ChR2 selectively expressed in 5-HTDRN neurons. Activation enhanced fear and anxiety, activating CRF neurons in BNST, inhibitory microcircuit underlying aversive behaviour following acute exposure to SSRI. CRF antagonism overcomes SSRI induced enhancements in aversive learning.

Question 4

Possible treatments

Answer 4

• retininitis pigementosa

- Seizures

Question 5

Tecuapetia (2010)

Answer 5

Nacc- Optogenetic activation of dopaminergic fibres (TH) and in vitro whole cell recording of spiny neurons that fast inward current blocked by AMPA antagonism. Showed independant of dopamine as blocked D1+D2 therefore not circuit.

Question 6

Stuber (2010)

Answer 6

Nacc- dopaminergic neuron activity could provoke glutamate-driven currents in recorded spiny neurons. Used VGLUT2 k/o in DA neurons- here light didn’t provoke EPSCs therefore VGLUT2 required for glutamate packaging.

Question 7

Tritsch (2012)

Answer 7

ChR2 expression in dopaminergic neurons and recording from spiny neurons in SNPc showed hyperpolarising effect. Others were under GABA blockade, two part effect illustrated by holding at Ecl. 2.2ms latency show direct effect. VGAT Cko unaffected but IPSCs inhibited with VMAT2 antagonist- monoamine transporter crucial in transporting NT + dopamine into vesicles

Question 8

Lammel (2015)

Answer 8

care when using mouse models with Cre-expression under specific promoter such as TH. TH expression varies widely from cell to cell. Varied but also dynamic, with respect to development, environment and epigenetics

Question 9

Zemmelman (2002)

Answer 9

Co-expression of drosophila photoreceptor genes (arrestin, rhodopsin, G protein subunit) sensitising neurons to light

Question 10

Boyden (2005)

Answer 10

Use of Chr2 to produce millisecond timescale genetically targeted optical control of neural activity with lentiviral gene delivery

Question 11

Kato (2012)

Answer 11

Crystal structure of channelrhodopsin channel. Describes retinal binding pocket - colour shifted variants, and cation conducting pathway- improve photocurrents, photosensitivity or selectivity

Question 12

Lin (2013)

Answer 12

ReaChr expressed in barrell motor cortex, driving spiking and motion in awake mice when excited by red light through intact skull. Illumination provided through external auditory canal, enabling transcranial activation of neurons in deep brain structures without the need to thin skull or make transcranial windows.

Question 13

Advantages of red light

Answer 13

Red light scattered less by tissue, absorbed less by blood