title: Sympathetic regulation and anterior cingulate cortex volume are altered in a rat model of chronic back pain.
abstract: Chronic pain is associated with autonomic disturbance. However, specific effects of chronic back pain on sympathetic regulation remain unknown. Chronic pain is also associated with structural changes in the anterior cingulate cortex (ACC), which may be linked to sympathetic dysregulation. The aim of this study was to determine whether sympathetic regulation and ACC surface and volume are affected in a rat model of chronic back pain, in which complete Freund Adjuvant (CFA) is injected in back muscles. Sympathetic regulation was assessed with renal blood flow (RBF) changes induced by electrical stimulation of a hind paw, while ACC structure was examined by measuring cortical surface and volume. RBF changes and ACC volume were compared between control rats and rats injected with CFA in back muscles segmental (T10) to renal sympathetic innervation or not (T2). In rats with CFA, chronic inflammation was observed in the affected muscles in addition to increased nuclear factor-kappa B (NF-kB) protein expression in corresponding spinal cord segments (p=0.01) as well as decreased ACC volume (p<0.05). In addition, intensity-dependent decreases in RBF during hind paw stimulation were attenuated by chronic pain at T2 (p's<0.05) and T10 (p's<0.05), but less so at T10 compared with T2 (p's<0.05). These results indicate that chronic back pain alters sympathetic functions through non-segmental mechanisms, possibly by altering descending regulatory pathways from ACC. Yet, segmental somato-sympathetic reflexes may compete with non-segmental processes depending on the back region affected by pain and according to the segmental organization of the sympathetic nervous system.
authors.affiliation: Department of Chiropractic, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada; CogNAC Research Group, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: Sara
authors.initials: S
authors.lastname: Touj
authors.affiliation: Department of Chiropractic, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Houle
authors.affiliation: Department of Chiropractic, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: Djamel
authors.initials: D
authors.lastname: Ramla
authors.affiliation: Department of Chiropractic, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada; CogNAC Research Group, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: Renaud
authors.initials: R
authors.lastname: Jeffrey-Gauthier
authors.affiliation: Department of Chiropractic, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada; Department of Autonomic Neuroscience, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo 173-0015, Japan.
authors.forename: Harumi
authors.initials: H
authors.lastname: Hotta
authors.affiliation: CogNAC Research Group, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada; Department of Anatomy, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: Gilles
authors.initials: G
authors.lastname: Bronchti
authors.affiliation: Department of Medical Biology, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: Maria-Grazia
authors.initials: MG
authors.lastname: Martinoli
authors.affiliation: Department of Chiropractic, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada; CogNAC Research Group, Université du Québec à Trois-Rivières, 3351 Boul. Des Forges, C.P. 500, Trois-Rivières, QC G9A 5H7, Canada. Electronic address: mathieu.piche@uqtr.ca.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Piché
mesh_terms: D000276:Adjuvants, Immunologic / Q000633:toxicity; D000818:Animals; D001342:Autonomic Nervous System Diseases / Q000209:etiology*; D064131:Back Muscles / Q000187:drug effects / Q000503:physiopathology; D001416:Back Pain / Q000139:chemically induced / Q000150:complications* / Q000473:pathology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D059350:Chronic Pain; D051545:Cyclooxygenase 1 / Q000378:metabolism; D004195:Disease Models, Animal; D004558:Electric Stimulation; D005620:Freund's Adjuvant / Q000633:toxicity; D006179:Gyrus Cinguli / Q000473:pathology*; D006614:Hindlimb / Q000294:innervation; D017078:Laser-Doppler Flowmetry; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D009220:Myositis / Q000209:etiology; D016328:NF-kappa B / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012079:Renal Circulation / Q000502:physiology*; D013116:Spinal Cord / Q000473:pathology
chemical_list: D000276:Adjuvants, Immunologic; D008565:Membrane Proteins; D016328:NF-kappa B; D005620:Freund's Adjuvant; D051545:Cyclooxygenase 1; C496513:Ptgs1 protein, rat
keywords: anterior cingulate cortex; chronic pain; neuroinflammation; nociception; somato-autonomic reflexes; sympathetic