μ-opioid receptor system mediates reward processing in humans.

Area of Science:

• Neuroscience
• Neuroimaging
• Obesity Research

Background:

• The endogenous μ-opioid receptor (MOR) system plays a crucial role in regulating motivational and hedonic processes.
• Understanding individual differences in the MOR system is vital for explaining variations in reward processing and eating behavior.

Purpose of the Study:

• To investigate the association between individual differences in MOR availability and neural reward responses to food cues in humans.
• To determine if MOR availability predicts brain activity in response to appetizing food stimuli.

Main Methods:

• Positron emission tomography (PET) with the MOR-specific radioligand [¹¹C]carfentanil was used to measure MOR availability in 33 non-obese individuals.
• Functional magnetic resonance imaging (fMRI) was employed to assess neural reward responses elicited by viewing appetizing versus bland food pictures.
• MOR availability in reward and emotion circuits was correlated with BOLD-fMRI responses to food stimuli.

Main Results:

• Viewing palatable food pictures, compared to bland ones, activated key reward and homeostatic processing regions, including the amygdala, ventral striatum, and hypothalamus.
• A significant negative association was found between MOR availability within the reward and emotion circuit and the fMRI-measured neural reward responses to food.
• Lower MOR availability predicted stronger neural activation in response to food cues.

Conclusions:

• Individual variations in MOR availability within the brain's reward circuitry are linked to differential neural responses to food stimuli.
• These findings suggest that MOR availability may contribute to the urge to eat when exposed to food cues, potentially influencing weight gain and obesity risk.