Inducing Peripheral Sympathetic Nerve Activity by Therapeutic Electrical Stimulation

Purpose. To examine whether the activity of peripheral sympathetic nerves in animals with spinal cord injury can be controlled using therapeutic electrical stimulation. Methods. The spinal cords of 6 Wistar rats were severed at T12/T13 disk level and were given continuous therapeutic electrical stimulation. Microneurography was used to record sympathetic nerve activity at 24, 48, and 72 hours after severing the spinal cord. Results. Integrated values of muscle sympathetic nerve activity after 72 hours of therapeutic electrical stimulation revealed significantly larger potentials on the stimulated side than the non-stimulated side. Skin sympathetic nerve activity showed no difference between the 2 sides. Conclusion. Therapeutic electrical stimulation was found to have a facilitatory effect on the muscle sympathetic nerve activity, whereas regulatory function was activated by the sympathetic nerves.

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Femoral vascular conductance and peroneal muscle sympathetic nerve activity responses to acute epidural spinal cord stimulation in humans

Experimental Physiology ◽

10.1113/ep086945 ◽

2018 ◽

Vol 103 (6) ◽

pp. 905-915 ◽

Cited By ~ 2

Author(s):

Seth W. Holwerda ◽

Marshall T. Holland ◽

Chandan G. Reddy ◽

Gary L. Pierce

Keyword(s):

Spinal Cord ◽

Sympathetic Nerve ◽

Spinal Cord Stimulation ◽

Sympathetic Nerve Activity ◽

Muscle Sympathetic Nerve Activity ◽

Vascular Conductance ◽

Nerve Activity ◽

Epidural Spinal Cord Stimulation

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Spinal regions involved in baroreflex control of renal sympathetic nerve activity in the rat

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00646.2010 ◽

2011 ◽

Vol 300 (4) ◽

pp. R910-R916 ◽

Cited By ~ 7

Author(s):

Matthew R. Zahner ◽

Lawrence P. Schramm

Keyword(s):

Spinal Cord ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Nerve Activity ◽

Thoracic Spinal Cord ◽

Renal Sympathetic Nerve Activity ◽

Sympathetic Control ◽

Renal Sympathetic Nerve ◽

Cord Injury ◽

Renal Sympathetic

Spinal cord injury causes debilitating cardiovascular disturbances. The etiology of these disturbances remains obscure, partly because the locations of spinal cord pathways important for sympathetic control of cardiovascular function have not been thoroughly studied. To elucidate these pathways, we examined regions of the thoracic spinal cord important for reflex sympathetic control of arterial pressure (AP). In anesthetized rats, baroreceptor relationships between pharmacologically induced changes in AP and changes in left renal sympathetic nerve activity (RSNA) were generated in spinally intact rats and after acute surgical hemisection of either the dorsal, left, or right T8 spinal cord. None of these individual spinal lesions prevented the baroreceptor-mediated increases in RSNA caused by decreases in AP. Thus, baroreceptor-mediated increases in RSNA in rats are mediated by relatively diffuse, bilateral, descending, excitatory projections. The ability to reduce RSNA at increased AP was impaired after both dorsal and left hemisections, and baroreceptor gain was significantly decreased. Baroreceptor-induced maximum decreases in RSNA were not affected by right hemisections. However, baroreflex gain was impaired. Because both dorsal and left hemisections, but not right hemisections, attenuated the decrease in RSNA at elevated AP, we conclude that pathways involved in the tonic inhibition of spinal sources of sympathetic activity descend ipsilaterally in the dorsal spinal cord. Our results show that many lesions that do not fully transect the spinal cord spare portions of both descending excitatory pathways that may prevent orthostatic hypotension and descending inhibitory pathways that reduce the incidence of autonomic dysreflexia.

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Ascending spinal pathways for the somatosympathetic A and C reflexes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1979.237.3.h342 ◽

1979 ◽

Vol 237 (3) ◽

pp. H342-H347

Author(s):

J. M. Chung ◽

C. L. Webber ◽

R. D. Wurster

Keyword(s):

Spinal Cord ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Silent Period ◽

Common Peroneal Nerve ◽

Sympathetic Nerves ◽

Nerve Activity ◽

C Fibers ◽

Ascending Pathways ◽

Spinal Pathway

Sympathetic unit nerve activity was recorded from the cervical sympathetic trunk of anesthetized, vagotomized, and carotid sinus-denervated cats. Single pulses or short trains of pulses with suprathreshold intensity for afferent C fibers were applied to the common peroneal nerve to elicit somatosympathetic A or simultaneous A and C reflexes, respectively. Bilateral lesions of an ascending spinal pathway in the dorsolateral sulcus area (DLS) of the T12 spinal cord eliminated the sympathetic C reflex. The remaining somatosympathetic A reflex was abolished by the subsequent lesion of an ascending spinal pathway in the dorsolateral funiculus (DLF) bilaterally. The duration of the silent period was found to be mainly influenced by an ascending spinal pathway in the DLF. It was concluded that excitation of afferent A fibers activates ascending pathways mainly in the DLF and a smaller contribution in the DLS of the spinal cord. This produces a small reflex excitation (A reflex) followed by a long silent period in the sympathetic nerves resulting in a net decrease of total sympathetic nerve activity. On the other hand, excitation of afferent C fibers activates the ascending spinal pathway in the DLS. This produces a reflex excitation (C reflex) which exceeds the decreased activity due to the silent period resulting in a net increase of total sympathetic nerve activity.

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Recovery of baroreflex control of renal sympathetic nerve activity after spinal lesions in the rat

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00295.2011 ◽

2011 ◽

Vol 301 (5) ◽

pp. R1584-R1590 ◽

Cited By ~ 9

Author(s):

Matthew R. Zahner ◽

Ewa Kulikowicz ◽

Lawrence P. Schramm

Keyword(s):

Spinal Cord ◽

Sympathetic Nerve ◽

Sympathetic Activity ◽

Sympathetic Nerve Activity ◽

Reflex Response ◽

Nerve Activity ◽

Renal Sympathetic Nerve Activity ◽

Renal Sympathetic Nerve ◽

Cord Injury ◽

Renal Sympathetic

Spinal cord injury (SCI) has serious long-term consequences on sympathetic cardiovascular regulation. Orthostatic intolerance results from insufficient baroreflex regulation (BR) of sympathetic outflow to maintain proper blood pressure upon postural changes. Autonomic dysreflexia occurs due to insufficient inhibition of spinal sources of sympathetic activity. Both of these conditions result from the inability to control sympathetic activity caudal to SCI. It is well established that limited motor ability recovers after incomplete SCI. Therefore, the goal of this study was to determine whether recovery of BR occurs after chronic, left thoracic spinal cord hemisection at either T3 or T8. Baroreflex tests were performed in rats by measuring the reflex response of left (ipsilateral) renal sympathetic nerve activity to decreases and increases in arterial pressure produced by ramped infusions of sodium nitroprusside and phenylephrine, respectively. One week after a T3 left hemisection, BR function was modestly impaired. However, 8 wk after a T3 left hemisection, BR function was normal. One week after a T8 left hemisection, BR function was significantly impaired, and 8 wk after a T8 left hemisection, BR function was significantly improved. These results indicate that BR of renal sympathetic nerve activity in rats may partially recover after spinal cord hemisections, becoming normal by 8 wk after a T3 lesion, but not after a T8 lesion. The nature of the spinal cord and/or brain stem reorganization that mediates this recovery remains to be determined.

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