Opioidergic modulation of monetary incentive delay fMRI responses

Area of Science:

• Neuroscience
• Pharmacology
• Neuroimaging

Background:

• Opioid reward effects are hypothesized to involve striatal dopaminergic signaling.
• The Monetary Incentive Delay (MID) task, a functional magnetic resonance imaging (fMRI) paradigm, assesses striatal responses during reward anticipation.

Purpose of the Study:

• To investigate if fentanyl modulates striatal Blood Oxygenation Level Dependent (BOLD) responses during the MID task.
• To explore opioidergic modulation of striatal dopaminergic signaling.

Main Methods:

• 24 male participants underwent fMRI while performing the MID task after receiving intravenous fentanyl, naloxone, or placebo.
• End-tidal CO2 was monitored to control for respiratory effects.

Main Results:

• Fentanyl increased MID task BOLD responses during reward and loss anticipation compared to placebo and naloxone.
• These fentanyl-induced increases were observed in cortical regions (e.g., lingual gyrus, precuneus) rather than the striatum.

Conclusions:

• Fentanyl primarily affected BOLD responses in regions related to motor response preparation, not striatal reward processing areas.
• Opioid agonists may not directly influence striatal activation in tasks like the MID.
• Future research may benefit from using naturalistic rewards to study opioid effects on reward processing, and findings are limited to male participants.