Selective opioid agonist and antagonist competition for [3H]-naloxone binding in amphibian spinal cord

Leslie C. Newman, David Wallace, Craig Stevens

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Opioids elicit antinociception in mammals through three distinct types of receptors designated as μ, κ and δ. However, it is not clear what type of opioid receptor mediates antinociception in non-mammalian vertebrates. Radioligand binding techniques were employed to characterize the site(s) of opioid action in the amphibian, Rana pipiens. Naloxone is a general opioid antagonist that has not been characterized in Rana pipiens. Using the non-selective opioid antagonist, [3H]-naloxone, opioid binding sites were characterized in amphibian spinal cord. Competitive binding assays were done using selective opioid agonists and highly-selective opioid antagonists. Naloxone bound to a single-site with an affinity of 11.3 nM and 18.7 nM for kinetic and saturation studies, respectively. A B(max) value of 2725 fmol/mg protein in spinal cord was observed. The competition constants (K(i)) of unlabeled μ, κ and δ ranged from 2.58 nM to 84 μM. The highly-selective opioid antagonists yielded similar K(i) values ranging from 5.37 to 31.1 nM. These studies are the first to examine opioid binding in amphibian spinal cord. In conjunction with previous behavioral data, these results suggest that non-mammalian vertebrates express a unique opioid receptor which mediates the action of selective μ, κ and δ opioid agonists. Copyright (C) 2000 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)184-191
Number of pages8
JournalBrain Research
Volume884
Issue number1-2
DOIs
StatePublished - 24 Nov 2000

Fingerprint

Narcotic Antagonists
Amphibians
Naloxone
Opioid Analgesics
Spinal Cord
Rana pipiens
Opioid Receptors
Vertebrates
Competitive Binding
Mammals
Binding Sites
Proteins

Keywords

  • Amphibian
  • Antinociception
  • NTI
  • Neurotransmitters, modulators, transporters, and receptors
  • Opioid
  • Opioid receptors
  • [H]-Naloxone
  • nor-BNI
  • β-FNA

Cite this

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abstract = "Opioids elicit antinociception in mammals through three distinct types of receptors designated as μ, κ and δ. However, it is not clear what type of opioid receptor mediates antinociception in non-mammalian vertebrates. Radioligand binding techniques were employed to characterize the site(s) of opioid action in the amphibian, Rana pipiens. Naloxone is a general opioid antagonist that has not been characterized in Rana pipiens. Using the non-selective opioid antagonist, [3H]-naloxone, opioid binding sites were characterized in amphibian spinal cord. Competitive binding assays were done using selective opioid agonists and highly-selective opioid antagonists. Naloxone bound to a single-site with an affinity of 11.3 nM and 18.7 nM for kinetic and saturation studies, respectively. A B(max) value of 2725 fmol/mg protein in spinal cord was observed. The competition constants (K(i)) of unlabeled μ, κ and δ ranged from 2.58 nM to 84 μM. The highly-selective opioid antagonists yielded similar K(i) values ranging from 5.37 to 31.1 nM. These studies are the first to examine opioid binding in amphibian spinal cord. In conjunction with previous behavioral data, these results suggest that non-mammalian vertebrates express a unique opioid receptor which mediates the action of selective μ, κ and δ opioid agonists. Copyright (C) 2000 Elsevier Science B.V.",
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Selective opioid agonist and antagonist competition for [3H]-naloxone binding in amphibian spinal cord. / Newman, Leslie C.; Wallace, David; Stevens, Craig.

In: Brain Research, Vol. 884, No. 1-2, 24.11.2000, p. 184-191.

Research output: Contribution to journalArticle

TY - JOUR

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