DREADDs: Chemogenetics Flashcards
What does DREADDs stand for?
Designer Receptors Exclusively Activated by Designer Drugs
What are DREADDs?
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
Why should we used DREADDs?
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
Chemogenetics allows us to observe..
The functionality of specific brain regions and the connections between multiple brain regions
Which cells are DREADDs most applicable to?
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
Where are DREADDs used?
Currently only in animal preclinical models
How are DREADDs used
- Labelled with fluorescent tag (e.g. GFP)
- Packaged in a viral construct (e.g. AAV)
- Virus administered to target brain area via aseptic stereotaxis surgery
- Designer ligand (e.g. CNO) can be administered via different routes
- Researcher performs the necessary testing
The first generation of DREADDs were based on…
the muscarinic ACh receptor
Activation DREADD
hM3Dq
Inhibition DREADD
hM4Di
How can AAV tropism be further altered?
By creating recombinant versions of multiple AAV serotypes (pseudotyping)
Which promoter drives transgene expression in neurons?
hSyn
Which promoter drives general transgene expression?
CAG
What is only expressed in tyrosine hydroxylase-containing cells?
Cre recombinase
What designer ligand is the inactive metabolite of Clozapine?
Clozapine N-oxide (CNO)
Clozapine is an agonist for
endogenous mACh receptors
What did DREADD technology demonstrate in AgRP neurons?
What did DREADD technology demonstrate in AgRP neurons?
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.
Ways to avoid important pitfalls with DREADDs
Test the specificity of the experimental conditions
Try to combine two DREADD ligands
Conventional pharmacological controls must be used
True or False: DREADDs are devoid of endogenous pharmacological activity.
False
