
<ArticleTitle>Differential [(3)H]idazoxan and [(3)H]2-(2-benzofuranyl)-2-imidazoline (2-BFI) binding to <prot>imidazoline I(2) receptor</prot>s in human postmortem frontal cortex.</ArticleTitle>
<AbstractText>[(3)H]2-(2-benzofuranyl)-2-imidazoline (2-BFI) and [(3)H]idazoxan are the most used tools to characterise <prot>imidazoline I(2) receptor</prot>s. We evaluated the binding of both radioligands to human postmortem frontal cortex membranes. Saturation binding analyses revealed that [(3)H]idazoxan (in the presence of 2 microM efaroxan to avoid radioligand binding to <prot>alpha(2)-adrenoceptor</prot>s and <prot>imidazoline I(1) receptor</prot>s) and [(3)H]2-BFI bound with high affinity to an apparent single population of sites. However, in competition studies whereas [(3)H]idazoxan (10 nM) binding was displaced monophasically by idazoxan and 2-BFI, both drugs displayed biphasic curves for [(3)H]2-BFI (1 nM). The proportion of the low-affinity binding site increased from 17% to 25% when 10 nM [(3)H]2-BFI was displaced by idazoxan. Amiloride inhibited [(3)H]2-BFI (10 nM) binding with low affinity and in a monophasic way. These data indicate that [(3)H]2-BFI recognises in human postmortem brain membranes a second binding site different from the <prot>imidazoline I(2) receptor</prot>s labelled by [(3)H]idazoxan.</AbstractText>
