Effects of corticospinal tract stimulation on renal sympathetic nerve activity in rats with intact and chronically lesioned spinal cords

Baohan Pan, Matthew R. Zahner, Ewa Kulikowicz, Lawrence P. Schramm

Research output: Contribution to journalArticlepeer-review

Abstract

Sympathetic preganglionic neurons and interneurons are closely apposed (presumably synapsed upon) by corticospinal tract (CST) axons. Sprouting of the thoracic CST rostral to lumbar spinal cord injuries (SCI) substantially increases the incidence of these appositions. To test our hypothesis that these additional synapses would increase CST control of sympathetic activity after SCI, we measured the effects of electrical stimulation of the CST on renal sympathetic nerve activity (RSNA) and arterial pressure (AP) in α-chloralose-anesthetized rats with either chronically intact or chronically lesioned spinal cords. Stimuli were delivered to the CST at intensities between 25-150 μA and frequencies between 25 and 75 Hz. Stimulation of the CST at the midcervical level decreased RSNA and AP. These decreases were not mediated by direct projections of the CST to the thoracic spinal cord because we could still elicit them by midcervical stimulation after acute lesions of the CST at caudal cervical levels. In contrast, caudal thoracic CST stimulation increased RSNA and AP. Neither the responses to cervical nor thoracic stimulation were affected by chronic lumbar SCI. These data show that the CST mediates decreases in RSNA via a cervical spinal system but excites spinal sympathetic neurons at caudal thoracic levels. Because chronic lumber spinal cord injury affected responses evoked from neither the cervical nor thoracic CST, we conclude that lesion-induced or regeneration-induced formation of new synapses between the CST and sympathetic neurons may not affect cardiovascular regulation.

Original languageEnglish (US)
Pages (from-to)R178-R184
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume293
Issue number1
DOIs
StatePublished - Jul 2007

Keywords

  • Cardiovascular regulation
  • Spinal cord injury
  • Sympathetic interneurons
  • Sympathetic preganglionic neurons

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Fingerprint Dive into the research topics of 'Effects of corticospinal tract stimulation on renal sympathetic nerve activity in rats with intact and chronically lesioned spinal cords'. Together they form a unique fingerprint.

Cite this