Chemogenetics revealed: DREADD occupancy and activation via converted clozapine

Area of Science:

• Neuroscience
• Pharmacology
• Molecular Biology

Background:

• Chemogenetic tools like DREADDs (designer receptors exclusively activated by designer drugs) enable remote control of neuronal activity.
• DREADDs are engineered receptors activated by specific ligands, commonly clozapine N-oxide (CNO).
• The precise in vivo mechanism of CNO action at DREADDs remains unconfirmed.

Purpose of the Study:

• To elucidate the in vivo mechanism of action for clozapine N-oxide (CNO) in DREADD-mediated chemogenetics.
• To investigate the role of clozapine, a metabolite of CNO, in DREADD activation.
• To confirm the brain penetration and DREADD affinity of CNO and clozapine.

Main Methods:

• Systemic administration of CNO and clozapine in animal models.
• Measurement of DREADD activation and neuronal activity.
• Pharmacokinetic analysis of CNO and clozapine distribution in the brain.

Main Results:

• CNO does not readily cross the blood-brain barrier and exhibits low affinity for DREADDs.
• CNO is rapidly metabolized to clozapine in vivo, which readily enters the brain.
• Clozapine demonstrates high affinity and potency for DREADDs, mediating DREADD-specific behaviors.

Conclusions:

• The chemogenetic effects attributed to CNO are primarily mediated by its active metabolite, clozapine.
• Clozapine, not CNO, is the key ligand engaging central nervous system DREADDs.
• This finding clarifies the mechanism of DREADD technology and informs future chemogenetic experimental design.