Binding capacities and affinities AT μ ∂ and k-opioid sites in membrane suspensions from Guinea-pig brain regions

Antonio La Regina, Monica Colombo, Paola Petrillo, Alessandra Tavani

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Binding capacities and affinities (KD) of ligands at μ ∂ and k-opioid binding sites were determined by selective labelling techniques together with analysis of saturation curves in seven regions of the guinea-pig brain. The k-sites predominated over the other sites in most regions and were 90% of the total in the cerebellum; binding capacities at ∂sites were highest in the cortex, intermediate in the cerebellum, striatum and mesencephalon and lowest in the diencephalon, hippocampus and pons-medulla. At the μsites, binding capacities were highest in the diencephalon and mesencephalon, with intermediate levels in the pons-medulla, cortex and striatum, and low levels in the hippocampus and cerebellum. The highest binding capacity at the ∂sites was in the striatum, intermediate in the cortex, diencephalon and hippocampus, low in the mesencephalon and pons-medulla and not detectable in the cerebellum. No regional differences in binding affinities were found at μ ∂ and k-sites with [3H]-[D-Ala2, MePhe4, Gly-ol5]enkephalin (KD = 1.10-2,61 nM), [3H]-[D-Ala2, D-Leu5]enkephalin (KD = 0.81-1.94 nM) and [3H]-(-)-bremazocine (KD = 0.083-0.185 nM). Thus in guinea-pig brain there are regional differences in opioid binding capacity and in the distribution of μ ∂ and k-sites, but not in binding affinities.

Original languageEnglish
Pages (from-to)171-180
Number of pages10
JournalJournal of Receptors and Signal Transduction
Issue number2
Publication statusPublished - 1992


  • Binding affinities
  • Binding capacities
  • Brain regions
  • Guinea-pig
  • Opioids
  • μpart;and k-opioid binding sites

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology
  • Pharmacology


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