title: [3H]naloxone as an opioid receptor label: analysis of binding site heterogeneity and use for determination of opioid affinities of casomorphin analogues.
abstract: The nonselective antagonist [3H]naloxone was used to identify opioid receptors in rat brain membranes. The multiple naloxone binding sites were related to different opioid receptors by means of selective opioid ligands as well as various beta-casomorphin analogues. Analysis of binding site heterogeneity was performed using several computer curve fitting methods. The results indicate that structurally modified casomorphin peptides are able to discriminate between mu 1- and mu 2-binding sites. The affinities to the mu-sites obtained with [3H]naloxone as label are in a good agreement with those from experiments with the mu-selective radioligand [3H]DAGO. The mu 1-site affinities of these casomorphin derivatives are well correlated with their antinociceptive potencies. This finding suggests the mediation of the analgesic activity via the high-affinity mu 1-subtype.
authors.affiliation: Department of Biology, Friedrich-Schiller University, Jena, GDR.
authors.forename: M
authors.initials: M
authors.lastname: Schnittler
authors.forename: C
authors.initials: C
authors.lastname: Liebmann
authors.forename: U
authors.initials: U
authors.lastname: Schrader
authors.forename: H P
authors.initials: HP
authors.lastname: Schulze
authors.forename: K
authors.initials: K
authors.lastname: Neubert
authors.forename: H
authors.initials: H
authors.lastname: Repke
mesh_terms: D000345:Affinity Labels / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004723:Endorphins / Q000378:metabolism*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D016308:Enkephalin, Leucine-2-Alanine; D004745:Enkephalins / Q000378:metabolism; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D009270:Naloxone / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000145:classification / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D000345:Affinity Labels; D004723:Endorphins; D004745:Enkephalins; D010446:Peptide Fragments; D011957:Receptors, Opioid; C034565:naloxone receptor; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009270:Naloxone; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; C021968:beta-casomorphins