Synthesis And Characterization Of125I-α-Conotoxin Arib[V11L;V16A] A Selective α7 Nicotinic Acetylcholine Receptor Antagonist
Department
neurobiology
Document Type
Article
Abstract
The α7 nicotinic acetylcholine receptors (nAChRs) are widely expressed both in the central nervous system (CNS) and periphery. In the CNS, 125I-α-bungarotoxin is commonly used to identify α7 nAChRs specifically. However, α-bungarotoxin also interacts potently with α1* and α9α10 nAChRs, two receptor subtypes in peripheral tissues that are colocalized with the α7 subtype. [ 3H]Methyllycaconitine is also frequently used as an α7-selective antagonist, but it has significant affinity for α6* and α9α10 nAChR subtypes. In this study, we have developed a highly α7-selective α-conotoxin radioligand by iodination of a naturally occurring histidine. Both mono- and diiodo derivatives were generated and purified (specific activities were 2200 and 4400 Ci mmol-1, respectively). The properties of the mono- and diiodo derivatives were very similar to each other, but the diiodo was less stable. For monoidodo peptide, saturation binding to mouse hippocampal membranes demonstrated a Kd value of 1.15 ± 0.13 nM, similar to that of 125I-α-bungarotoxin in the same preparations (0.52 ± 0.16 nM). Association and dissociation kinetics were relatively rapid (k obs for association at 1 nM was 0.027 ± 0.007 min -1; koff = 0.020 ± 0.001 min-1). Selectivity was confirmed with autoradiography using α7-null mutant tissue: specific binding was abolished in all regions of α7-/- brains, whereas wild-type mice expressed high levels of labeling and low nonspecific binding. 125I-α-conotoxin ArIB[V11L; V16A] should prove useful where α7 nAChRs are coexpressed with other subtypes that are also labeled by existing ligands. Furthermore, true equilibrium binding experiments could be performed on α7 nAChRs, something that is impossible with 125I-α-bungarotoxin. Copyright © 2008 by The American Society for Pharmacology and Experimental Therapeutics.
Publication Date
6-1-2008
Publication Title
Journal of Pharmacology and Experimental Therapeutics
ISSN
00223565
Volume
325
Issue
3
First Page
910
Last Page
919
Digital Object Identifier (DOI)
10.1124/jpet.108.136895
Recommended Citation
Whiteaker, Paul; Marks, Michael J.; Christensen, Sean; Dowell, Cheryl; Collins, Allan C.; and McIntosh, J. Michael, "Synthesis And Characterization Of125I-α-Conotoxin Arib[V11L;V16A] A Selective α7 Nicotinic Acetylcholine Receptor Antagonist" (2008). Translational Neuroscience. 394.
https://scholar.barrowneuro.org/neurobiology/394