Interaction of endogenous opioid peptides and other drugs with four kappa opioid binding sites in guinea pig brain

• Published in: Peptides (New York, N.Y. : 1980) Vol. 11; no. 2; pp. 311 - 331
• Main Authors: Rothman, Richard B, Bykov, Victor, de Costa, Brian R, Jacobson, Arthur E, Rice, Kenner C, Brady, Linda S
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.03.1990; Elsevier Science
• Subjects: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Affinity Labels; Affinity ligands; Analysis of Variance; Animals; Autoradiography; Benzeneacetamides; Benzomorphans - metabolism; Biological and medical sciences; Brain - metabolism; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; Data Interpretation, Statistical; Endorphins - metabolism; Enkephalin, Ala-MePhe-Gly; Enkephalins - metabolism; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Kappa opioid receptors; Ligands; Male; Mathematics; Membranes - metabolism; Naltrexone - analogs & derivatives; Naltrexone - metabolism; Pyrrolidines - metabolism; Receptor autoradiography; Receptor binding; Receptors, Opioid - metabolism; Receptors, Opioid, kappa; Temperature; U50,488; U69,593; Vertebrates: nervous system and sense organs; α-Neoendorphin; β-Endorphin(1–31); U50,488; U69,593; Kappa opioid receptors; β-Endorphin(1–31); α-Neoendorphin; Receptor autoradiography; Receptor binding; Affinity ligands; Brain; Ligand binding; Interaction; Rodentia; Central nervous system; Acylation agent; Binding site; Neuropeptide; Opioid peptide; Opiate receptor; Autoradiography; Vertebrata; Mammalia; Guinea pig
• ISSN: 0196-9781; 1873-5169
• DOI: 10.1016/0196-9781(90)90088-M

Guinea pig brain membranes depleted of μ and δ receptors by pretreatment with the site-directed acylating agents, 2-(4-ethoxybenzyl)-1-diethylaminoethyl-5-isothiocyanatobenzimidazole·HCl (BIT) and N-phenyl-N-[1-(2-(4-isothiocyanato)phenethyl)-4-piperidinyl]-propanamide·HCl (FIT), were used in this study to test the hypothesis that guinea pig brain possesses subtypes of κ receptors. Pretreatment of membranes with either (−)-(1 S,2 S)-U50,488 or the κ selective acylating agent, (1 S,2 S)-trans-2-isothiocyanato-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide, caused a wash-resistant inhibition of κ 1 binding sites labeled by [ 3H]U69,593 binding, but not κ 2 binding sites labeled by [ 3H]bremazocine. Binding surface analysis of [ 3H]bremazocine binding resolved two binding sites, termed κ 2a and κ 2b, present at densities of 212 and 225 fmol/mg protein, which had low affinity for (−)-(1 S,2 S)-U50,488 and U69,593. The κ 2b site had high affinity for β-endorphin(1–31) (K d=5.5 nM) and [D-Ala 2,D-Leu 5]enkephalin (K d=14 nM), and lower affinity for [D-Ala 2-MePhe 4,Gly-ol 5]enkephalin (K d=147 nM) and [Leu 5]enkephalin (K d=46.0 nM). Binding surface analysis of [ 3H]U69,593 binding also resolved two binding sites, termed κ 1a and κ 1b, present at densities of 6.0 and 40.0 fmol/mg protein. The κ 1a binding site was characterized by very high affinity for α-neoendorphin. Quantitative autoradiographic studies demonstrated that κ 2a and κ 2b binding sites are heterogeneously distributed in guinea pig brain, and that the anatomical distribution of κ 1 binding sites reported in the literature is different from that observed in this study for the κ 2 binding sites. Viewed collectively, these data provide evidence for four κ receptor subtypes in guinea pig brain.