Rate constants of agonist binding to muscarinic receptors in rat brain medulla. Evaluation by competition kinetics
The method of competition kinetics, which measures the binding kinetics of an unlabeled ligand through its effect on the binding kinetics of a labeled ligand, was employed to investigate the kinetics of muscarinic agonist binding to rat brain medulla pons homogenates. The agonists studied were acetylcholine, carbamylcholine, and oxotremorine, with N-methyl-4-(TH)piperidyl benzilate employed as the radiolabeled ligand. Our results suggested that the binding of muscarinic agonists to the high affinity sites is characterized by dissociation rate constants higher by 2 orders of magnitude than those of antagonists, with rather similar association rate constants. Our findings also suggest that isomerization of the muscarinic receptors following ligand binding is significant in the case of antagonists, but not of agonists. Moreover, it is demonstrated that in the medulla pons preparation, agonist-induced interconversion between high and low affinity bindings sites does not occur to an appreciable extent.
- Research Organization:
- Tel Aviv Univ., Israel
- OSTI ID:
- 6334485
- Journal Information:
- J. Biol. Chem.; (United States), Vol. 15
- Country of Publication:
- United States
- Language:
- English
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PARASYMPATHOMIMETICS
RADIORECEPTOR ASSAY
ACETYLCHOLINE
BIOCHEMICAL REACTION KINETICS
BRAIN
CHOLINE
HOMOGENATES
IN VITRO
PIPERIDINES
RATS
RECEPTORS
TRITIUM COMPOUNDS
ALCOHOLS
AMINES
AMMONIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZINES
BODY
CENTRAL NERVOUS SYSTEM
DRUGS
ESTERS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LIPOTROPIC FACTORS
MAMMALS
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PYRIDINES
QUATERNARY COMPOUNDS
REACTION KINETICS
RODENTS
TRACER TECHNIQUES
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics