Purpose:
The aim of this study was to test whether applying transient (range 10-60 min) compression to the upper cervical spinal cord modulates somatic evoked reflex activity in the adrenal nerve.
Methods:
Experiments were performed on spontaneously breathing adult Wistar rats (n=5; 380-430g) initially anaesthetized with urethane (1.3g/kg i.p.) and supplemented (i.v.) to maintain absence of withdrawal and palpebral reflexes. Venous and arterial canulas provided fluids and a record of arterial blood pressure. Averaged adrenal nerve activity was recorded in response to electrical stimulation (1Hz, 5 X 0.5ms square wave pulses) of the ipsilateral sciatic nerve at ≥ 1.5X threshold (T) for muscle twitch, while static compression was applied using a probe (2.3 X 2.8 mm) placed on the dorsal surface of the exposed, dura intact, upper cervical spinal cord.
Results:
High intensity (≥ 15T) stimuli evoked a reflex response (onset latency range 50-100ms; duration ~120ms) in each rat’s stimulus- triggered averaged (n=500) adrenal nerve recordings. Applied pressure ranging (1.13-3.92g) from that sufficient to compress the dura so it just contacted the dorsal surface of the cord to that necessary to occlude the vessels on the dorsal surface of the cord, induced a reduction (range 12-35%) in the amplitude of the somatic evoked adrenal nerve response. When tested up to 60 min after removing the probe, the somatic evoked responses were present but remained reduced in amplitude
Conclusion:
In the anaesthetized rat, static transient (< 60 min) compression of the upper cervical spinal cord can reduce somatic afferent induced activity in the adrenal nerve and it remains reduced for more than an hour after compression has been removed.
Grant Value: $26,752
Chief Investigator: Dr Philip Bolton – University of Newcastle
Status: Completed
Publications:
- The Spine Journal Volume 15, Issue 6, June 2015
Bigland, Mark J. et al. The influence of cervical spinal cord compression and vertebral displacement on somatosympathetic reflexes in the rat 1310 – 1317
Posters:
- Australian Neuroscience Society January 2010. Sydney, Australia
Budgell BS, Bolton PS Somato-adrenal reflex and upper cervical spinal cord compression-a pilot study. P-083, Page 150
Presentations:
- Department of Chiropractic, Faculty of Science Macquarie University 2013. Sydney, Australia
Bolton. PS., What do lab-based neurophysiological studies tell us about the chiropractor’s vertebral subluxation hypothesis? - Research Symposium Annual National Conference, Chiropractors Association of Australia 2011 Melbourne, Australia
Bolton PS Investigation of the chiropractic vertebral subluxation hypothesis – An update on the physiological impacts of spinal cord compression in an animal model