Distinct Thalamo-Subcortical Circuits Underlie Painful Behavior and Depression-Like Behavior Following Nerve Injury

Area of Science:

• Neuroscience
• Behavioral Science
• Pathophysiology

Background:

• Chronic pain and depression frequently co-occur, worsening patient outcomes and complicating treatment.
• The underlying neural mechanisms driving this comorbidity are not fully understood.
• Identifying specific brain circuits involved is crucial for developing targeted therapies.

Purpose of the Study:

• To elucidate the distinct neural circuit mechanisms in the paraventricular thalamus (PVT) that contribute to the comorbidity of chronic pain and depression.
• To differentiate the roles of specific PVT subregions and their downstream targets in mediating pain and depression-like behaviors.

Main Methods:

• Utilized a spared nerve injury (SNI) model to induce chronic pain and depression-like behaviors.
• Investigated glutamatergic neurons in the posterior PVT (PVP^Glu) projecting to the ventrolateral periaqueductal gray (VLPAG^GABA).
• Examined glutamatergic neurons in the anterior PVT (PVA^Glu) projecting to nucleus accumbens D1/D2-positive neurons (NAc^D1→D2).

Main Results:

• The PVP^Glu→VLPAG^GABA circuit was found to mediate pain-related behaviors in the context of the comorbidity.
• The PVA^Glu→NAc^D1→D2 circuit was identified as being involved in depression-like behaviors.
• These distinct thalamo-cortical pathways differentially regulate pain and depression phenotypes following SNI.

Conclusions:

• The study reveals two distinct thalamo-subcortical circuits within the PVT that independently control pain and depression-like behaviors.
• These findings provide crucial insights into the circuit-level basis of chronic pain and depression comorbidity.
• The identified circuits represent potential novel targets for the prevention and treatment of comorbid chronic pain and depression.