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This Article Full Text Full Text (PDF) All Versions of this Article: 90/4/2548    most recent 00999.2002v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Kang, Y. M. Articles by Pickar, J. G. Search for Related Content PubMed PubMed Citation Articles by Kang, Y. M. Articles by Pickar, J. G.

Somatosympathetic Reflexes From the Low Back in the Anesthetized Cat

¹ Palmer College of Chiropractic, Palmer Center for Chiropractic Research, Davenport 52803; ² Department of Biomedical Engineering and Iowa Spine Research Center, University of Iowa, Iowa City, Iowa; ³ Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas; ⁴ University of Iowa, Iowa Testing Programs and UI Back Care, Iowa City, Iowa

Submitted 1 November 2002; accepted in final form 30 May 2003

In the appendicular skeleton, substantial evidence demonstrates that somatosensory input from deep tissues including limb muscles and joints elicits somatosympathetic reflexes. Much less is known about the presence and organization of these reflexes from the axial skeleton. We determined if mechanical loading of the lumbar spine and lumbar paraspinal muscle irritation reflexively affects postganglionic sympathetic nerve discharge (SND) to the spleen and kidney. In 27 -chloralose-anesthetized cats, the L_2–4 multifidus muscles were injected with the inflammatory irritant mustard oil (20%, 60 µl total) and a vertebral load (100% body weight) was applied dorsal-ventral at the L₃ spinous process. Mustard oil injection alone without vertebral loading (n = 7) increased mean splenic SND (60%), renal SND (30%), and heart rate (HR; 52 bpm). Mustard oil injection accompanied by the vertebral load (n = 7) increased mean splenic SND (55%), renal SND (16%), and HR (27 bpm). Blood pressure changes were biphasic and could not account for these changes. When the vertebral load accompanied mustard oil, the increases in splenic SND, renal SND, and HR remained elevated in a pattern significantly different from when the vertebral load was absent. Vehicle injection combined with the mechanical load (n = 3) did not change any of the autonomic responses. Similarly, mustard oil injection combined with a mechanical load did not change these responses when either the medial branches of the dorsal rami from T₁₁–L₅ had been cut (n = 4) or when the spinal cord had been transected between the second and third cervical vertebrae (n = 6). The results indicate that inflammatory stimulation of multifidus muscle in the low back evokes a somatosympathetic reflex integrated supraspinally in the upper cervical spinal cord or higher. The reflex's afferent arm travels in the medial branch of the dorsal ramus, and its efferent arm can affect sympathetic outflow to the spleen and the kidney as well as HR and BP. A static mechanical load applied to the lumbar spine accompanying the inflammatory stimulus appears to sustain the inflammatory-induced reflex activity.