Hypoalgesia induced by blockade of noradrenergic projections to the raphe magnus: reversal by blockade of noradrenergic projections to the spinal cord

Jacqueline Sagen, Herbert K. Proudfit

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

Previous studies have demonstrated that microinjection of noradrenergic (NA) antagonists such as phentolamine in the nucleus raphe magnus (NRM) produces hypoalgesia. This hypoalgesia appears to result from disinhibition of raphe-spinal serotonergic neurons since it is blocked by intrathecally injected methysergide. The present studies demonstrate that the hypoalgesia produced by microinjection of phentolamine in the NRM is also abolished by intrathecal administration of phentolamine. The results suggest that the hypoalgesia produced by microinjection of NA antagonists in the NRM is also mediated, at least in part, by the activation of spinally projecting NA neurons. Such hypoalgesia does not appear to be mediated by activation of enkephalinergic neurons since intrathecal injection of the opiate antagonist naloxone did not attenuate the hypoalgesia.

Original languageEnglish (US)
Pages (from-to)391-396
Number of pages6
JournalBrain Research
Volume223
Issue number2
DOIs
StatePublished - Nov 2 1981
Externally publishedYes

Keywords

  • brain stem
  • hypoalgesia
  • noradrenergic
  • nucleus raphe magnus
  • phentolamine
  • spinal cord

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

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