Nociception in pigeons is not impaired by capsaicin

Janós Szolcsányi, Holger Sann, Friedrich Karl Pierau

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Abstract

In order to examine the sensitivity of the nociceptive system of birds to capsaicin, the algesic potency of the drug was compared with that of veratridine and mustard oil by instillation into the eye of conscious pigeons and guinea-pigs. In guinea-pigs, 10-6 g/ml capsaicin provoked severe protective reactions, but even high concentrations of 10 -2 g/ml were insufficient in pigeons. Veratridine and mustard oil induced similar reactions in both species. Close arterial injections of algesic substances revealed that the threshold dose of capsaicin for cardiovascular and nocifensive reactions was 10,000-fold higher in pigeons (200 μg) than in guinea-pigs (0.02 μg). All other algesic substances tested (bradykinin, 5-HT, veratridine and KC1) had similar thresholds in both species. Slow infusion of a total dose of 600 mg/kg capsaicin into the radial artery of pigeons did not alter the sensitivity to any of the algesic substances tested, which demonstrates that even high concentrations of capsaicin have no desensitizing effect. The demonstrated insensitivity of pigeons to the algesic effect of capsaicin is discussed in the context of the inability of the drug to deplete substance P (SP) from afferent terminals in the spinal cord of the pigeon.

Original languageEnglish
Pages (from-to)247-260
Number of pages14
JournalPain
Volume27
Issue number2
DOIs
Publication statusPublished - Nov 1986

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Keywords

  • capsaicin
  • nociception
  • pigeon

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Anesthesiology and Pain Medicine

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