Characterisation of kappa-opioid binding sites in rat and guinea-pig spinal cord

Neuropharmacology. 1989 Oct;28(10):1041-6. doi: 10.1016/0028-3908(89)90115-9.


The binding of radiolabelled ligands with high affinity for kappa-opioid binding sites has been studied in homogenates of lumbo-sacral spinal cord from the rat. The unselective ligands [3H]bremazocine and [3H]diprenorphine labelled a large number of sites which could not be fully resolved in terms of mu-, delta- and kappa-types by displacement assays. In particular binding at the kappa-site appeared anomalous in that sites which could be identified as high affinity kappa-type represented only 40% of total kappa-binding, defined using the unselective [3H]ligands. This was confirmed by the low levels of binding seen with the kappa-agonists [3H]dynorphin A(1-9) and [3H]U-69593. In guinea-pig cord, under conditions in which binding to mu- and delta-sites was suppressed, [3H]dynorphin A(1-9) and [3H]U-69593 labelled only 60% of the kappa population, defined by the [3H]unselective ligands. The reasons for the observed discrepancies are discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzeneacetamides*
  • Benzomorphans / metabolism
  • Captopril / pharmacology
  • Diprenorphine / metabolism
  • Dynorphins / metabolism
  • Guinea Pigs
  • In Vitro Techniques
  • Leucine / pharmacology
  • Ligands
  • Male
  • Peptide Fragments / metabolism
  • Pyrrolidines / metabolism
  • Rats
  • Rats, Inbred Strains
  • Receptors, Opioid / metabolism*
  • Receptors, Opioid, kappa
  • Spinal Cord / metabolism*


  • Benzeneacetamides
  • Benzomorphans
  • Ligands
  • Peptide Fragments
  • Pyrrolidines
  • Receptors, Opioid
  • Receptors, Opioid, kappa
  • Diprenorphine
  • Dynorphins
  • dynorphin A (1-9)
  • Captopril
  • Leucine
  • ubenimex
  • bremazocine
  • U 69593