Imidazole binding sites in rabbit kidney and forebrain membranes.

1. The binding of [3H]-clonidine, [3H]-idazoxan and [3H]-yohimbine to rabbit forebrain and kidney membranes was compared. 2. Yohimbine bound exclusively to adrenergic sites, idazoxan to non-adrenergic sites and clonidine to both non-adrenergic and adrenergic sites. 3. Differences were observed between the ligands not only in binding at adrenergic and non-adrenergic sites but also between the non-adrenergic binding of [3H]-clonidine and [3H]-idazoxan. 4. However, no tissue specific differences were found.