Midbrain dopamine drives splenic immunity through a brain-to-body circuit

Area of Science:

• Neuroscience
• Immunology
• Neuroimmunology

Background:

• Midbrain dopamine neurons are crucial for central nervous system functions.
• Emerging evidence suggests their influence extends to peripheral immune systems.

Purpose of the Study:

• To elucidate the neural circuit connecting midbrain dopamine neurons to the spleen.
• To investigate the immunomodulatory effects of activating this pathway.

Main Methods:

• Tracing neural pathways from midbrain dopamine neurons to the spleen.
• In vivo activation of midbrain dopamine neurons.
• Measuring dopamine release, neuronal activity (immediate early gene expression), spleen weight, and T-cell populations.

Main Results:

• A multisynaptic pathway from midbrain dopamine neurons to the spleen via the dorsal vagal complex and celiac ganglion was identified.
• Activation of this circuit led to dopamine release in the dorsal vagal complex and increased neuronal activity in the pathway.
• Activation reduced spleen weight and decreased naïve CD4+ T-cell populations, but not total T-cells.

Conclusions:

• A functional midbrain-dorsal vagal complex-celiac ganglion-spleen pathway exists.
• Midbrain dopamine neurons can directly modulate splenic immunity through this circuit.
• This pathway represents a potential target for immunotherapeutic interventions in diseases with altered dopamine neurotransmission.