[3H]dynorphin1-8 binding sites in frog (Rana esculenta) brain membranes

S. Benyhe, J. Simon, A. Borsodi, M. Wollemann, E. A. Barnard

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Opioid binding sites specific for [3H]dynorphin1-8 were characterized in the particulate membrane fraction of frog (Rana esculenta) brain. The degradation of the radioligand during the assay was prevented by the use of a broad spectrum of peptidase inhibitors. The binding of [3H]dynorphin1-8 to frog brain membranes was stereoselective, reversible, saturable, and displaceable by a series of opioid ligands including dynorphin1-13, bremazocine, levorphanol and naloxone. The specific binding of [3H]dynorphin1-8 can be significantly inhibited by Na+ ions and/or guanine nucleotides confirming the agonist property of the ligand in vitro. A single set of high affinity opioid binding sites with a Kd ≈ 7.5 nM is present in the membranes. The maximum density of binding sites (Bmax ≈ 1.1 pmol [3H]dynorphin1-8 per mg protein) was considerably higher than such sites in guinea-pig brain. In addition, comparison with binding of tritiated opioid peptides selective for the μ- and σ-types of opioid receptor showed that in the frog brain most of the sites labelled by [3H]dynorphin1-8 are κ-sites and that this is a rich source of such sites.

Original languageEnglish
Pages (from-to)359-364
Number of pages6
Issue number5
Publication statusPublished - May 1994


ASJC Scopus subject areas

  • Endocrinology
  • Neurology
  • Endocrine and Autonomic Systems
  • Cellular and Molecular Neuroscience

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