DREADDs: Chemogenetics

Question 1

What does DREADDs stand for?

Answer 1

Designer Receptors Exclusively Activated by Designer Drugs

Question 2

What are DREADDs?

Answer 2

Engineered GPCRs that can be controlled remotely by the researcher using specific ligands i.e. can activate or inhibit the cell they are expressed in

Question 3

Why should we used DREADDs?

Answer 3

There are a lot of disorders, especially in relation to the brain which are still vastly misunderstood
NB psychiatric disorders

This is why this technique is currently widely employed in neuroscience research

Question 4

Chemogenetics allows us to observe..

Answer 4

The functionality of specific brain regions and the connections between multiple brain regions

Question 5

Which cells are DREADDs most applicable to?

Answer 5

Neurons - they are always in a state of activation or inhibition

Allows us to observe the implications of these changes in activity on a cellular level, and in a circuit function, as well as on anatomical physiology and behaviour as well

Question 6

Where are DREADDs used?

Answer 6

Currently only in animal preclinical models

Question 7

How are DREADDs used

Answer 7

1. Labelled with fluorescent tag (e.g. GFP)
2. Packaged in a viral construct (e.g. AAV)
3. Virus administered to target brain area via aseptic stereotaxis surgery
4. Designer ligand (e.g. CNO) can be administered via different routes
5. Researcher performs the necessary testing

Question 8

The first generation of DREADDs were based on…

Answer 8

the muscarinic ACh receptor

Question 9

Activation DREADD

Answer 9

hM3Dq

Question 10

Inhibition DREADD

Answer 10

hM4Di

Question 11

How can AAV tropism be further altered?

Answer 11

By creating recombinant versions of multiple AAV serotypes (pseudotyping)

Question 12

Which promoter drives transgene expression in neurons?

Answer 12

hSyn

Question 13

Which promoter drives general transgene expression?

Answer 13

CAG

Question 14

What is only expressed in tyrosine hydroxylase-containing cells?

Answer 14

Cre recombinase

Question 15

What designer ligand is the inactive metabolite of Clozapine?

Answer 15

Clozapine N-oxide (CNO)

Question 16

Clozapine is an agonist for

Answer 16

endogenous mACh receptors

Question 17

What did DREADD technology demonstrate in AgRP neurons?

Question 18

What did DREADD technology demonstrate in AgRP neurons?

Answer 18

That activation of AgRP neurons rapidly and dramatically induces feeding, reduces energy expenditure and ultimately increases fat stores. In contrast, inhibiting AgRP neurons in hungry mice reduced food intake.

Question 19

Ways to avoid important pitfalls with DREADDs

Answer 19

Test the specificity of the experimental conditions
Try to combine two DREADD ligands
Conventional pharmacological controls must be used

Question 20

True or False: DREADDs are devoid of endogenous pharmacological activity.

Answer 20

False