An endogenous opioid circuit determines state-dependent reward consumption

Area of Science:

• Neuroscience
• Behavioral Science
• Pharmacology

Background:

• Mu-opioid peptide receptor (MOPR) stimulation influences critical functions like respiration, pain relief, and reward.
• Dysregulation of MOPR signaling is implicated in substance abuse and overdose.
• The endogenous mechanisms by which MOPR controls consummatory behaviors remain largely unelucidated.

Purpose of the Study:

• To investigate the endogenous MOPR regulatory mechanisms governing reward consumption.
• To identify the specific neural circuits involved in MOPR-mediated control of consummatory behavior.

Main Methods:

• Utilized a mouse model to study MOPR regulation of reward consumption.
• Investigated a specific dorsal raphe to nucleus accumbens projection.
• Employed selective modulation of nucleus accumbens enkephalin neurons.
• Applied CRISPR-Cas9 gene editing to disrupt enkephalin production.

Main Results:

• Discovered that MOPR regulation of reward consumption in mice relies on a dorsal raphe to nucleus accumbens pathway.
• Demonstrated that MOPR-mediated inhibition of raphe terminals is both necessary and sufficient for controlling consummatory responses.
• Identified enkephalin-containing nucleus accumbens ensembles activated before reward consumption, indicating local enkephalin as the endogenous MOPR ligand source.

Conclusions:

• Isolated a fundamental endogenous opioid circuit essential for state-dependent consumptive behaviors.
• This circuit involves a specific dorsal raphe to nucleus accumbens projection and local enkephalin release.
• Findings suggest novel strategies for modulating reward pathways and treating substance abuse.