title: The influence of cervical spinal cord compression and vertebral displacement on somatosympathetic reflexes in the rat.
abstract: BACKGROUND
  One theory within chiropractic proposes that vertebral subluxation in the upper cervical region induces spinal cord compression sufficient to alter spinal cord efferent output. We report on the feasibility of three different experimental approaches to test this theory.
  
  
  METHODS
  A high threshold electrical-evoked somatosympathetic reflex was recorded in adrenal or renal nerves of 10 anaesthetized adult male rats before and after (1) graded pressure was applied directly to the C1/C2 spinal cord segment in eight rats by the use of either direct compression or inflation of an extradural balloon and (2) displacement, less than a dislocation applied posterior to anterior, to the C2 vertebra in two rats. The latency and amplitude of the pre- and postintervention reflex responses were compared.
  
  
  RESULTS
  The reflex amplitude was not significantly changed by pressure (26 mmHg) from an extra-dural balloon or direct compression of the dura mater onto the dorsal spinal cord. Additional pressure, at least sufficient to occlude the dorsal vessels, induced a significant reduction in the amplitude of the reflex, and this reduction persisted for 20 minutes after removal of the pressure (Dunn's method for all pairwise multiple comparison Q stat=3.437; critical value for k=6 with α=0.05 is 2.936). Maximal vertebral (C2) displacement (4 mm), without dislocation did not induce significant changes compared with the control period.
  
  
  CONCLUSIONS
  Although this feasibility study suggests it is unlikely that upper cervical vertebral subluxation, displacement less than a dislocation, compromises the sympathetic outflow in the adrenal or renal nerves, further vertebral displacement studies are necessary to formally test this.
authors.affiliation: School of Biomedical Sciences & Pharmacy, Faculty of Health and Medicine, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Bigland
authors.affiliation: Canadian Memorial Chiropractic College, 6100 Leslie St, Toronto, ON M2H3J1, Canada.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Budgell
authors.affiliation: School of Biomedical Sciences & Pharmacy, Faculty of Health and Medicine, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia; Priority Research Centre for Translational Neuroscience and Mental Health, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia. Electronic address: Philip.Bolton@newcastle.edu.au.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Bolton
mesh_terms: D000818:Animals; D002574:Cervical Vertebrae / Q000503:physiopathology*; D004388:Dura Mater / Q000503:physiopathology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000502:physiology*; D013117:Spinal Cord Compression / Q000503:physiopathology*
keywords: Chiropractic; Rat; Somato-sympathetic reflex; Spinal cord; Vertebral subluxation