Objective: The role of the nucleus accumbens (NAc) in chronic neuropathic pain has been suggested, but the role of the NAc in dorsal root ganglion (DRG) neuropathic pain remains unclear. The objective of this study was to determine whether optogenetic stimulation of the NAc influences DRG compression-induced neuropathic pain.
Materials and methods: We established sham or DRG lesions in female Sprague-Dawley rats by L4-5 DRG root compression, and the animals received unilateral injections of optogenetic virus in the NAc core. We employed reflexive pain tests to assess the alterations between the groups at the light on/off states. To determine thalamic firing, we performed single-unit in vivo extracellular recording. For statistical analysis, we used one- or two-way repeated-measures analysis of variance.
Results: Compared to sham-operated rats, chronic compressed DRG rats showed elevated behavioral sensitivity and sustained neuronal hyperexcitability in the thalamus. NAc optic stimulation improved pain behaviors and lowered thalamic discharge from ventral posterolateral thalamic nuclei.
Conclusions: The NAc core impacts the reward and motivational aspects of chronic neuropathic pain influenced by limbic behaviors to thalamic discharge. Increased thalamic firing activity may result in chronic compressed DRG-induced neuropathic pain, and optogenetic neuromodulation of the NAc can ease chronic pain and thalamic discharge.
Keywords: DRG; emotion; neuropathic pain; nucleus accumbens; optogenetics.
© 2019 International Neuromodulation Society.