Is substance P a primary afferent neurotransmitter for nociceptive input? I. Analysis of pain-related behaviors resulting from intrathecal administration of substance P and 6 excitatory compounds

Hanan Frenk, Daniel Bossut, Gideon Urca, David J. Mayer

Research output: Contribution to journalArticlepeer-review

Abstract

Intrathecal (i.t.) injection of substance P (SP), capsaicin, kainic acid, picrotoxin, strychnine, morphine, and l-glutamic acid in rats induced rhythmic scratching movements with the hindlimbs, biting, and, with some of these compounds, vocalization and myoclonic twitches. Although biting was directed to the dermatome corresponding to the injection site, scratching was aimed at anterior dermatomes. Presumably painful chemical stimulation produced by cutaneous and subcutaneous application of capsaicin or acetic acid never elicited scratching. Vocalization was never elicited by SP. When vocalization occurred following i.t. picrotoxin and morphine, it was correlated with myoclonic twitches rather than with scratching and/or biting. These findings indicate that scratching (a) is not pain-related and, (b) when elicited by the i.t. administration of the compounds listed above, does not result from activation of nociceptive primary afferent synapses.

Original languageEnglish
Pages (from-to)223-231
Number of pages9
JournalBrain Research
Volume455
Issue number2
DOIs
StatePublished - 12 Jul 1988

Keywords

  • Behavior
  • Capsaicin
  • Kainic acid
  • Morphine
  • Pain
  • Picrotoxin
  • Spinal cord
  • Strychnine
  • Substance P
  • l-Glutamic acid

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