Quantitative analysis of multiple kappa-opioid receptors by selective and nonselective ligand binding in guinea pig spinal cord: Resolution of high and low affinity states of the kappa 2 receptors by a computerized model-fitting technique

Journal Article · Tue May 01 00:00:00 EDT 1990 · Molecular Pharmacology; (USA)

OSTI ID:6749572

Tiberi, M; Magnan, J ^[1]

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1. Universite de Montreal, Quebec (Canada)

The binding characteristics of selective and nonselective opioids have been studied in whole guinea pig spinal cord, using a computer fitting method to analyze the data obtained from saturation and competition studies. The delineation of specific binding sites labeled by the mu-selective opioid (3H)D-Ala2,MePhe4,Gly-ol5-enkephalin (Kd = 2.58 nM, R = 4.52 pmol/g of tissue) and by the delta-selective opioid (3H)D-Pen2, D-Pen5-enkephalin (Kd = 2.02 nM, R = 1.47 pmol/g of tissue) suggests the presence of mu and delta-receptors in the spinal cord tissue. The presence of kappa receptors was probed by the kappa-selective opioid (3H)U69593 (Kd = 3.31 nM, R = 2.00 pmol/g of tissue). The pharmacological characterization of the sites labeled by (3H)U69593 confirms the assumption that this ligand discriminates kappa receptors in guinea pig spinal cord. The benzomorphan (3H)ethylketazocine labels a population of receptors with one homogeneous affinity state (Kd = 0.65 nM, R = 7.39 pmol/g of tissue). The total binding capacity of this ligand was not different from the sum of the binding capacities of mu, delta-, and kappa-selective ligands. Under mu- and delta-suppressed conditions, (3H)ethylketazocine still binds to receptors with one homogeneous affinity state (Kd = 0.45 nM, R = 1.69 pmol/g of tissue). Competition studies performed against the binding of (3H)ethylketazocine under these experimental conditions reveal that the pharmacological profile of the radiolabeled receptors is similar to the profile of the kappa receptors labeled with (3H)U69593. Saturation studies using the nonselective opioid (3H)bremazocine demonstrate that this ligand binds to spinal cord membranes with heterogeneous affinities (Kd1 = 0.28 nM, R1 = 7.91 pmol/g of tissue; Kd2 = 3.24 nM, R2 = 11.2 pmol/g of tissue).

• OSTI ID: 6749572
• Journal Information: Molecular Pharmacology; (USA), Vol. 37:5; ISSN 0026-895X
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ENDORPHINS
RECEPTORS
BIOCHEMICAL REACTION KINETICS
CELL MEMBRANES
COMPUTERIZED SIMULATION
GUINEA PIGS
LIGANDS
QUANTITATIVE CHEMICAL ANALYSIS
RADIOASSAY
SPINAL CORD
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
CELL CONSTITUENTS
CENTRAL NERVOUS SYSTEM
CHEMICAL ANALYSIS
DRUGS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
PROTEINS
REACTION KINETICS
RODENTS
SIMULATION
VERTEBRATES
550201* - Biochemistry- Tracer Techniques