Background <p>Pain is a prevalent and frequently undertreated non-motor symptom in Parkinson’s disease (PD), affecting approximately 40% to 85% of patients. The zona incerta (ZI) is primarily an inhibitory subthalamic region involved in nociceptive neurotransmission. Previous studies demonstrated that the ZI is an important gamma-aminobutyric acid-ergic (GABAergic) source to the ventral tegmental area (VTA), but whether the ZI-VTA pathway participates in PD pain processing is still unclear. Given that deep brain stimulation targeting the ZI has demonstrated beneficial effects on pain perception in PD patients, we hypothesized that GABAergic signaling within the ZI may play a critical role in PD pain hypersensitivity.</p> Methods <p>Male C57BL/6 mice and Vgat-Cre mice were used in the experiments. A unilateral PD mouse model was established through the injection of 6-hydroxydopamine (6-OHDA) into the striatum. We performed von Frey test and hot/cold plate tests to assess nociceptive behavior in PD mice. We then employed fiber photometry, chemogenetic, and optogenetic approaches to investigate the roles of ZI GABAergic neurons and ZI<sup>GABA</sup>-VTA circuit on PD pain hypersensitivity.</p> Results <p>Activation of ZI GABAergic neurons alleviated pain hypersensitivity in PD mouse model, whereas inhibition of these neurons was sufficient to induce pain hypersensitivity in control naïve mice. Furthermore, we demonstrated that projections from GABAergic neurons in the ZI to VTA are involved in regulating pain associated with PD. Chemogenetic and optogenetic activation of the ZI<sup>GABA</sup>-VTA circuit alleviated pain symptoms; conversely, inhibiting activity within this circuit exacerbated both mechanical and thermal pain hypersensitivity.</p> Conclusions <p>Our results indicate that the ZI GABAergic neurons and their downstream projections to the VTA play crucial roles in modulating pain processing under both physiological conditions and during PD states. This research offers fresh perspectives on the PD pain mechanism. Considering our previous report indicating that stimulation of ZI GABAergic neurons improved motor performance in 6-OHDA-lesioned mice, we propose that the ZI may serve a dual regulatory function concerning both motor behavior and pain response associated with PD.</p> Graphical Abstract <p></p>

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Activation of the zona incerta GABAergic circuit for the treatment of pain hypersensitivity in Parkinson’s disease mice model

  • Juntao Cui,
  • Junliang Qian,
  • Yaying Shi,
  • Yanhong Liu,
  • Le Qu,
  • Wenting Jia,
  • Junxia Xie,
  • Limin Shi

摘要

Background

Pain is a prevalent and frequently undertreated non-motor symptom in Parkinson’s disease (PD), affecting approximately 40% to 85% of patients. The zona incerta (ZI) is primarily an inhibitory subthalamic region involved in nociceptive neurotransmission. Previous studies demonstrated that the ZI is an important gamma-aminobutyric acid-ergic (GABAergic) source to the ventral tegmental area (VTA), but whether the ZI-VTA pathway participates in PD pain processing is still unclear. Given that deep brain stimulation targeting the ZI has demonstrated beneficial effects on pain perception in PD patients, we hypothesized that GABAergic signaling within the ZI may play a critical role in PD pain hypersensitivity.

Methods

Male C57BL/6 mice and Vgat-Cre mice were used in the experiments. A unilateral PD mouse model was established through the injection of 6-hydroxydopamine (6-OHDA) into the striatum. We performed von Frey test and hot/cold plate tests to assess nociceptive behavior in PD mice. We then employed fiber photometry, chemogenetic, and optogenetic approaches to investigate the roles of ZI GABAergic neurons and ZIGABA-VTA circuit on PD pain hypersensitivity.

Results

Activation of ZI GABAergic neurons alleviated pain hypersensitivity in PD mouse model, whereas inhibition of these neurons was sufficient to induce pain hypersensitivity in control naïve mice. Furthermore, we demonstrated that projections from GABAergic neurons in the ZI to VTA are involved in regulating pain associated with PD. Chemogenetic and optogenetic activation of the ZIGABA-VTA circuit alleviated pain symptoms; conversely, inhibiting activity within this circuit exacerbated both mechanical and thermal pain hypersensitivity.

Conclusions

Our results indicate that the ZI GABAergic neurons and their downstream projections to the VTA play crucial roles in modulating pain processing under both physiological conditions and during PD states. This research offers fresh perspectives on the PD pain mechanism. Considering our previous report indicating that stimulation of ZI GABAergic neurons improved motor performance in 6-OHDA-lesioned mice, we propose that the ZI may serve a dual regulatory function concerning both motor behavior and pain response associated with PD.

Graphical Abstract