[125I]CGP 42112 reveals a non-angiotensin II binding site in 1-methyl-4-phenylpyridine (MPP+)-induced brain injury.

1. Intracerebral injection of the oxidative metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-methyl-4-phenylpyridine (MPP+), into the substantia nigra of adult rats resulted in a lesion at the injection site. 2. Using autoradiography, we localized specific [125I]CGP 42112 binding that was not recognized by angiotensin II or angiotensin II AT1 or AT2 receptor-selective ligands. 3. Our results suggest that [125I]CGP 42112 may be binding to activated microglia that appear at the lesion site.