Orexin-immunoreactive inputs to rat sympathetic preganglionic neurons

I. J. Llewellyn-Smith, C. L. Martin, J. N. Marcus, Masashi Yanagisawa, J. B. Minson, T. E. Scammell

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


Orexin increases blood pressure and orexin-immunoreactive (IR) axons robustly innervate the spinal cord. Seeking anatomical evidence for direct effects of orexin on sympathetic preganglionic neurons (SPN), we used immunohistochemistry to study the relationships between orexin-IR axons and SPN identified by immunoreactivity for choline acetyltransferase (ChAT) or for cholera toxin B retrogradely transported from the superior cervical ganglion (SCG). In the intermediolateral cell column (IML), varicose, orexin-positive axons closely apposed almost all SPN in segments T1 and T2, but appositions were rare in T4-L2. Orexin fibers also apposed ChAT-IR cell bodies in the intercalated nucleus and the central autonomic area from T1 to L2. Orexin-IR synapses were identified ultrastructurally on SPN projecting to the SCG. Since SPN involved in cardiovascular control cluster in the IML of mid- and lower thoracic cord, these findings suggest that orexin affects blood pressure by acting on supraspinal neurons rather than SPN.

Original languageEnglish (US)
Pages (from-to)115-119
Number of pages5
JournalNeuroscience letters
Issue number2
StatePublished - Nov 13 2003


  • Autonomic regulation
  • Blood pressure
  • Hypocretin
  • Immunocytochemistry
  • Spinal cord
  • Superior cervical ganglion
  • Ultrastructure

ASJC Scopus subject areas

  • Neuroscience(all)


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