[3H]2-(2-benzofuranyl)-2-imidazoline: a new selective high affinity radioligand for the study of rabbit brain imidazoline I2 receptors.
This is the first study characterising the binding of the new imidazoline I2 receptor selective radioligand [3H]2-(2-benzofuranyl)-2-imidazoline (2-BFI) to rabbit brain membranes. [3H]2-BFI binding was found to be saturable and of high affinity identifying two binding sites with KD1 = 0.27 nM, Bmax = 111.2 fmol mg-1 protein and KD2 = 8.97 nM, Bmax = 268 fmol mg-1 protein. Specific binding represented greater than 90% of total binding. Kinetic studies revealed that the binding was rapid and reversible and also showed [3H]2-BFI interacted with these two sites or two affinity states. In competition binding studies against [3H]2-BFI (0.3-InM) idazoxan, 2-BFI, cirazoline, guanabenz, naphazoline, amiloride and BU224 (2-(4,5-dihydroimidaz-2-yl-quinoline) displaced with high affinity. In contrast the alpha 2-adrenoceptor antagonists efaroxan and rauwolscine, the I1 site selective drug moxonidine, the monoamine oxidase-A inhibitor clorgyline and the proposed endogenous imidazoline receptor ligand, agmatine, were weak at displacing [3H]2-BFI binding. These findings are consistent with [3H]2-BFI recognising imidazoline receptors of the I2 subtype in rabbit brain.
Lione
L A
LA
Department of Pharmacology, School of Medical Sciences, University of Bristol, UK.
Nutt
D J
DJ
Hudson
A L
AL
D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D001572:Benzofurans / Q000378:metabolism*; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D007093:Imidazoles / Q000378:metabolism*; D054755:Imidazoline Receptors; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D011485:Protein Binding; D011817:Rabbits; D011869:Radioligand Assay; D011955:Receptors, Drug / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000345:Affinity Labels; D001572:Benzofurans; D007093:Imidazoles; D054755:Imidazoline Receptors; D011955:Receptors, Drug; C103723:2-(2-benzofuranyl)-2-imidazoline