Opiate microinjections into midbrain do not affect the aversiveness of caudal trigeminal stimulation but produce somatotopically organized peripheral hypoalgesia

Glenn S. Kasman, J. Peter Rosenfeld*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

High-dose microinjections of morphine sulfate (15 μg) and (d-Ala2)-Met-enkephalin (30μg) were made into the ventral periaqueductal gray of cats. Consistent with previous reports using lower doses, both opiates produced hypoalgesia for noxious thermal stimuli applied to the upper and lower body. More hypoalgesia was observed on the face than on the hind legs or tail. Current thresholds of aversive reaction to stimulation in the trigeminal subnucleus caudalis were unaffected by microinjection of either opiate. Systemic injections of 6 mg/kg morphine sulfate profoundly inhibited defense responses to peripheral noxious stimuli and significantly elevated aversive reaction thresholds for stimulation in the trigeminal subnucleus caudalis. Aversive reactions to stimulation in the dorsal periaqueductal gray remained unaffected by either microinjected or systemically administered opiates.

Original languageEnglish (US)
Pages (from-to)271-278
Number of pages8
JournalBrain research
Volume383
Issue number1-2
DOIs
StatePublished - Sep 24 1986

Keywords

  • Analgesia
  • Hypoalgesia
  • Morphine
  • Opiate
  • Pain
  • Periaqueductal gray
  • Trigeminal nucleus

ASJC Scopus subject areas

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

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