Peyton Presto¹, Julian Cardenas¹, Christian Bustamante¹, Brent Kisby^1,2, Guangchen Ji^1,2, Olga Ponomareva¹, Volker Neugebauer^1,2,3*, Igor Ponomarev^1,2*

Neuropathic pain is a chronic pain condition that results from damage or dysfunction in the nervous system. While mechanisms of neuropathic pain at the peripheral and spinal cord level have been extensively studied, pain mechanisms in the brain remain underexplored. The amygdala, a limbic brain region, has emerged as a critical brain area for the emotional-affective dimension of pain and pain modulation. Amygdala neuroplasticity has been associated with pain states, but exact molecular and cellular mechanisms underlying these states and the transition from acute to chronic pain are not well understood. Here, we used the spinal nerve ligation model of neuropathic pain in male rats to investigate changes in gene expression in two amygdala nuclei, basolateral (BLA) and central (CeA) at the chronic pain stage using RNA sequencing. We used an integrative approach that focuses on functional significance and cell type specificity of differentially expressed genes to nominate mechanistic targets for central regulation of chronic pain. Our integrative transcriptomic and bioinformatic analyses identified individual genes (e.g., Cxcl10, Cxcl12, Mbp, Plp1, Mag, Mog, Slc17a6, Gad1, Sst), molecular pathways (e.g., cytokine-mediated signaling pathway), biological processes (e.g., myelination, synaptic transmission), and specific cell types (e.g., oligodendrocytes, glutamatergic and GABAergic neurons) affected by chronic pain. Our results also provide evidence for hemispheric lateralization of pain processing in the amygdala. Overall, our study proposes oligodendrocyte dysfunction in the amygdala, neuroimmune signaling in the CeA, and glutamatergic neurotransmission in the BLA as mechanistic determinants of and potential therapeutic targets for the management of chronic neuropathic pain.

1. Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, 3601 4^th Street, Lubbock, Texas 79430, U.S.A. 2. Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, 3601 4^th Street, Lubbock, Texas 79430, U.S.A. 3. Garrison Institute on Aging, Texas Tech University Health Sciences Center, 3601 4^th Street, Lubbock, Texas 79430, U.S.A.

Funding Support: National Institutes of Health grants R01 NS038261 to V.N. and I.P. and R01 AA027096 to I.P.