An Approach for Assaying Benzodiazepine Receptor Binding with Radioiodinated Ligand : ¹²⁵I-Labeled Diazepam Derivative

Abstract

[¹²⁵I]2'-Iododiazepam (IDZ) was prepared and its application in a benzodiazepine receptor binding assay was studied. [¹²⁵I]2'-IDZ binds to the rat cortical membrane with a high affinity (K_d, 0.66 nM). Various benzodiazepines showed competition with [¹²⁵I]2'-IDZ for the binding sites in the rat cortical membrane, and the specificity of its binding correlated well with that of [³H]diazepam (r=0.992, p<0.001). These findings suggested that [¹²⁵I]2'-IDZ binds to the same sites as [³H]diazepam and indicated that [¹²⁵I]2'-IDZ can be used in a benzodiazepine receptor assay.