Lower Muscarinic M1 Receptor Availability in Schizophrenia: In Vivo PET Evidence.

Area of Science:

• Neuroscience
• Psychiatry
• Radiochemistry

Background:

• Growing evidence links brain muscarinic M1 receptors to schizophrenia neurobiology.
• Postmortem studies indicate M1 receptor deficits in schizophrenia patients.
• The recent FDA approval of xanomeline (M1/M4 agonist) for schizophrenia highlights M1 receptor's therapeutic potential.

Purpose of the Study:

• To quantify in vivo brain M1 receptor availability in schizophrenia patients using a novel PET ligand.
• To investigate the relationship between M1 receptor availability and clinical features in schizophrenia.

Main Methods:

• Utilized the PET ligand 11C-LSN3172176 for in vivo M1 receptor quantification.
• Compared M1 availability (DVR_CS and V_T) in 16 schizophrenia patients and 16 healthy controls.
• Accounted for regional gray matter fraction (%GM) to control for potential atrophy.

Main Results:

• Schizophrenia patients showed significantly lower M1 availability across multiple brain regions (e.g., frontal, temporal, caudate) compared to controls.
• Large effect sizes observed for M1 availability deficits in cortical and subcortical areas.
• A subgroup of patients exhibited more pronounced whole-brain M1 deficits; exploratory analyses suggested clinical correlations.

Conclusions:

• In vivo findings confirm significant M1 receptor deficits in schizophrenia, consistent with postmortem data.
• M1 receptors represent a promising therapeutic target for schizophrenia.
• M1 receptor availability may serve as a potential biomarker for guiding muscarinic-based treatments.