Abstract
The \(\mu\)-opioid receptor (MOP) is crucial for both the therapeutic and addictive effects of opioids. Using a multimodal experimental approach, here we combined awake functional ultrasound (fUS) imaging with behavioral and molecular assessments, to examine opioid-induced changes in brain activation and functional connectivity (FC). Morphine, fentanyl, and methadone induce significant dose- and time-dependent reorganization of brain perfusion, oscillations and FC in awake mice. Notably, opioids induce a transient, region-specific hyperperfusion, followed by a consistent MOP-specific dysconnectivity marked by decreased FC of the somatosensory cortex to hippocampal and thalamic regions, alongside increased subcortical and intra-cortical FC. These FC changes temporally correlate with generalized brain MOP activation and analgesia, but not with hypermobility and respiratory depression, suggesting a reorganization of inter-regional FC as a key opioid effect.