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Somatosympathetic reflexes from the low back in the anesthetized cat
Y M Kang1, M J Kenney, K F Spratt
1Palmer College of Chiropractic, Palmer Center for Chiropractic Research, Iowa, Davenport 52803, USA.
Journal of Neurophysiology
|June 13, 2003
Summary
Inflammation in the low back muscles triggers a sympathetic nerve reflex affecting spleen and kidney function. Mechanical spine loading sustained this reflex, indicating supraspinal integration.
Area of Science:
- Neuroscience
- Physiology
- Skeletal Biology
Background:
- Somatosympathetic reflexes are well-documented from appendicular structures.
- Little is known about these reflexes originating from the axial skeleton, particularly the lumbar spine.
Purpose of the Study:
- To investigate if mechanical loading and lumbar paraspinal muscle irritation reflexively affect sympathetic nerve discharge (SND) to the spleen and kidney.
- To determine the neural pathways involved in these reflexes.
Main Methods:
- Used alpha-chloralose-anesthetized cats.
- Injected L2-4 multifidus muscles with mustard oil (inflammatory irritant) and applied a mechanical load to the L3 vertebra.
- Measured splenic and renal SND, heart rate (HR), and blood pressure.
- Performed surgical interventions including dorsal ramus cutting and spinal cord transection.
Main Results:
- Mustard oil injection alone increased splenic SND (60%), renal SND (30%), and HR (52 bpm).
- Combined mustard oil and mechanical loading sustained elevated splenic SND, renal SND, and HR.
- Neural pathway analysis indicated supraspinal integration via the medial branches of the dorsal rami.
Conclusions:
- Inflammatory stimulation of lumbar multifidus muscle evokes a somatosympathetic reflex.
- This reflex is integrated supraspinally and involves afferent pathways in the medial dorsal rami.
- Mechanical lumbar spine loading appears to sustain inflammatory-induced reflex activity, impacting sympathetic outflow to organs and cardiovascular parameters.