enkephalin--leucine-2-alanine and tifluadom

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Enkephalin, D-Penicillamine (2,5)-; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Enkephalins; Male; Mice; Mice, Inbred ICR; Naltrexone; Narcotic Antagonists; Oligopeptides; Pyrrolidines; Receptors, Opioid; Vas Deferens

By selectively blocking cross-interferences from other types of binding sites, a binding site which likely represents kappa opioid binding sites was obtained in the guinea-pig brain suspension of the particulate fraction. Selective ligands for mu, sigma, delta and epsilon opioid binding sites were poor inhibitors for inhibiting [3H]ethylketocyclazocine binding to this site, whereas kappa opioids like oxilorphan, dynorphin(1-13), ethylketocyclazocine, butorphanol, cyclazocine, ketocyclazocine, tifluadom, nalorphine, pentazocine, U-50-488, nalbuphine and naloxone were potent ligands. Buprenorphine, generally believed to be a mu opiate, was the most potent inhibitor at the kappa site. Scatchard analysis of the saturation curve of [3H]ethylketocyclazocine binding revealed two subtypes of kappa binding sites: a high-affinity site and a low-affinity site with Kd = 0.7 and 78 nM and maximum binding = 22 and 101 fmol/mg of protein, respectively. Analysis of the inhibition curves suggested that tifluadom may be a selective ligand for the high-affinity site and that dynorphin(1-13) and U-50-488 may bind preferentially the high-affinity site but still possess appreciable affinity for the low-affinity site. This study demonstrates a selective assay for kappa opioid binding sites and indicates a possibility of the heterogeneity of kappa opioid binding sites in the brain.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Binding Sites; Brain; Cyclazocine; Dynorphins; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Ethylketocyclazocine; Etorphine; Guinea Pigs; Levallorphan; Peptide Fragments; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Stereoisomerism

Topics: Animals; Benzodiazepines; Benzomorphans; Electrophysiology; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Hippocampus; In Vitro Techniques; Male; Narcotics; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa

3H-Tifluadom labels specifically recognition sites of opioid kappa receptors. Membranes of guinea-pig whole brain bind 3H-tifluadom with two affinities, in contrast to the cerebellum where almost all opioid sites are kappa.

Topics: Animals; Benzodiazepines; Benzomorphans; Binding Sites; Brain; Cyclazocine; Dihydromorphine; Dynorphins; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Enkephalins; Ethylketocyclazocine; Guinea Pigs; In Vitro Techniques; Male; Morphine; Receptors, Opioid