Elsevier

Life Sciences

Volume 59, Issue 1, 31 May 1996, Pages PL23-PL29
Life Sciences

Pharmacology letter accelerated communication
Orphanin FQ: Receptor binding and analog structure activity relationships in rat brain

https://doi.org/10.1016/0024-3205(96)00261-5Get rights and content

Abstract

A tritiated form of orphanin FQ (a heptadecapeptide also known as Nociceptin) has been prepared. This radioligand (33 Ci/mmole) was used to develop a radioreceptor assay using rat brain homogenates. Binding was observed to be saturable, and analyses of the binding data indicate the presence of a single binding site with a dissociation constant of 5 ± 1.1 nM and Bmax of 535 ± 85 fmoles/mg protein. Thirty-four analogues of orphanin FQ, including a complete alanine “scan” of orphanin FQ, and truncation analogues from both the N- and C- terminals were synthesized and tested. The data obtained indicate that the N-terminus plays a more critical role in binding than the C-terminus and that residues 1, 2, 4, and 8 are essential for binding.

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