Chronic Morphine Leaves a Durable Fingerprint on Whole-Brain Functional Connectivity.

Area of Science:

• Neuroscience
• Pharmacology
• Addiction Research

Background:

• Opioid use disorder (OUD) is a chronic, relapsing condition where brain adaptations to opioids complicate abstinence.
• Studying brain dysfunction during OUD abstinence is challenging, with human neuroimaging yielding inconsistent results.

Purpose of the Study:

• To investigate whole-brain functional connectivity (FC) in a mouse model of morphine abstinence.
• To identify brain regions and network alterations associated with opioid abstinence and morphine exposure.

Main Methods:

• Utilized a mouse model of morphine abstinence combined with functional magnetic resonance imaging (fMRI).
• Assessed whole-brain functional connectivity at rest and during acute morphine challenge.
• Employed hierarchical clustering, seed-to-voxel analysis, random forest classification, and dynamic FC analysis.

Main Results:

• Abstinent mice exhibited widespread, condition-independent alterations in functional connectivity.
• The retrosplenial cortex and amygdala were identified as key markers of abstinence.
• A persistent morphine signature involving cortical and midbrain components was detected in abstinent mice at rest.
• Abstinent animals showed amplified and accelerated brain-wide FC reactivity to acute morphine challenge.

Conclusions:

• Chronic opioid exposure induces a durable pharmacological signature on brain communication.
• Findings have implications for understanding and managing pain and recovery from opioid use disorder.