Polyclonal anti-idiotypic antibodies to idazoxan and their interaction with human brain imidazoline binding sites

Polyclonal antibodies were raised in rabbits against purified polyclonal anti-idazoxan antibodies. The anti-idiotypic antibodies thus obtained, proved able to inhibit [H-3]idazoxan specific binding to anti-idazoxan antibodies. Applied to human nucleus reticularis lateralis membrane preparations, these antibodies (20 mu g) inhibited about 50 and 70% of the imidazoline specific binding of [H-3]idazoxan and [H-3]clonidine, respectively. Furthermore, they specifically immunoprecipitated 50% of [H-3]idazoxan binding activity of imidazoline binding sites solubilized from the same tissue. [H-3]Rauwolscine binding to alpha(2)-adrenoceptors in rat cortex was not significantly affected by these antibodies. The antibodies labeled a 43 kDa protein in Western blots of partially purified imidazoline binding sites from human brain. In conclusion, these anti-idiotypic antibodies recognize imidazoline binding sites from human brain and allow the detection of a 43 kDa binding protein associated with or representing the imidazoline receptor expressed in human brain.