A Neural Circuit for Gut-Induced Reward.

Area of Science:

• Neuroscience
• Gastroenterology
• Psychiatry

Background:

• The gut's role in regulating emotional and motivational states is increasingly recognized.
• However, the specific neural circuits connecting the gut to the brain's reward system remain largely uncharacterized.

Purpose of the Study:

• To elucidate the gut-brain neuronal circuitry underlying reward.
• To investigate the role of vagal sensory neurons in mediating reward pathways.

Main Methods:

• Optical activation of gut-innervating vagal sensory neurons.
• Behavioral assays for self-stimulation, flavor, and place conditioning.
• Cell-specific transneuronal tracing.
• Dopamine release measurement in the Substantia nigra.

Main Results:

• Activation of the right vagal sensory ganglion, but not the left, sustained self-stimulation behavior and induced reward.
• This activation led to dopamine release in the Substantia nigra and conditioned preferences.
• Transneuronal tracing identified a specific pathway from the right vagal sensory ganglion, through the dorsolateral parabrachial region, to Substantia nigra dopamine cells.
• Activating this parabrachio-nigral projection mimicked the rewarding effects of right vagus stimulation.

Conclusions:

• The vagal gut-to-brain axis is a critical component of the brain's neuronal reward pathway.
• These findings suggest that targeting vagal pathways could offer novel therapeutic strategies for affective disorders.