Non-competitive binding of the nonpeptide antagonist BIBP3226 to rat forebrain neuropeptide Y1 receptors

• Published in: European journal of pharmacology Vol. 331; no. 2-3; pp. 275 - 284
• Main Authors: VANDERHEYDEN, P. M. L, VAN LIEFDE, I, DE BACKER, J.-P, VAUQUELIN, G
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 23.07.1997
• Subjects: Animals; Arginine - analogs & derivatives; Arginine - metabolism; Binding, Competitive - drug effects; Biological and medical sciences; Cell receptors; Cell structures and functions; Fundamental and applied biological sciences. Psychology; Guanylyl Imidodiphosphate - pharmacology; Half-Life; In Vitro Techniques; Membranes - drug effects; Membranes - metabolism; Molecular and cellular biology; Nerve Tissue Proteins - metabolism; Neuropeptide receptors; Neuropeptide Y - metabolism; Prosencephalon - metabolism; Proteins - metabolism; Radioligand Assay; Rats; Receptors, Neuropeptide Y - antagonists & inhibitors; Receptors, Neuropeptide Y - metabolism; Neuropeptide Y; Peptide hormone; Central nervous system; Non peptide compound; Binding site; Frontal cortex; In vitro; Biological fixation; Structure activity relation; Neurotransmitter; Peptidergic receptor; Models; Antagonist; Coupling; Brain (vertebrata); G protein
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(97)01016-9

[3H]Neuropeptide Y labelled neuropeptide Y receptors in rat forebrain membranes as a homogenous class of high-affinity sites. Between 80 and 85% of these receptors showed high affinity for Y1-selective antagonists such as (R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-D-arginine amide (BIBP3226). While competitive in functional studies, BIBP3226 produced parallel shifts of the Scatchard plots of [3H]neuropeptide Y saturation binding in rat forebrain membranes. Mechanisms which are routinely invoked to explain non-competitive binding do not apply to BIBP3226. Wash-out experiments, involving successive treatment of the membranes with BIBP3226, buffer (wash-out step) and [3H]neuropeptide Y, argue against irreversible or a pseudo-irreversible binding of the antagonist. Allosteric inhibition is also unlikely since BIBP3226 did not affect the rate of dissociation of [3H]neuropeptide Y in isotope dilution experiments. The non-hydrolyzable guanine nucleotide, 5'-guanylylimidodiphosphate (Gpp(NH)p), abolished the binding of [3H]neuropeptide Y and increased its rate of dissociation in isotope dilution experiments. This suggests that the initial [3H]neuropeptide Y-receptor association is a low affinity process and that the observed binding of [3H]neuropeptide Y is related to the formation of a ternary [3H]neuropeptide Y-receptor-G protein complex. Two- or even multistate models (in which BIBP3226 could potentially behave as an inverse agonist) could therefore be needed to explain the non-competitive antagonism of BIBP3226 in broken cell preparations.