Potentiation of the lateral habenula-ventral tegmental area pathway underlines the susceptibility to depression in mice with chronic pain

Chronic pain often develops severe mood changes such as depression. However, how chronic pain leads to depression remains elusive and the mechanisms determining individuals' responses to depression are largely unexplored. Here we found that depression-like behaviors could only be observed in 67.9% of mice with chronic neuropathic pain, leaving 32.1% of mice with depression resilience. We determined that the spike discharges of the ventral tegmental area (VTA)-projecting lateral habenula (LHb) glutamatergic (Glu) neurons were sequentially increased in sham, resilient and susceptible mice, which consequently inhibited VTA dopaminergic (DA) neurons through a LHb(Glu)-VTA(GABA)-VTA(DA) circuit. Furthermore, the LHb(Glu)-VTA(DA) excitatory inputs were dampened via GABA(B) receptors in a pre-synaptic manner. Regulation of LHb-VTA pathway largely affected the development of depressive symptoms caused by chronic pain. Our study thus identifies a pivotal role of the LHb-VTA pathway in coupling chronic pain with depression and highlights the activity-dependent contribution of LHb(Glu)-to-VTA(DA) inhibition in depressive behavioral regulation.

Automated summary

Chronic pain can lead to depression, but the specific mechanisms are still unclear. This study found that only 67.9% of mice with chronic neuropathic pain exhibited depression-like behaviors, while 32.1% of mice showed resilience to depression. The study highlights the importance of the connection between two groups of neurons in the development of depressive symptoms caused by chronic pain.