Subunit composition of striatal nAChRs. A, B, Solubilized striatal membrane extracts from α6-/-, α4-/-, α6+/+, and α4+/+ mice, preincubated with 2 nm³H-Epi, were immunoprecipitated with subunit-specific Abs. Results are expressed in femtomoles of immunoprecipitated ³H-Epi/mg of protein (n = 3-5; ^*p < 0.05 compared with matching Wt control; Student's t test). Total ³H-Epi and ¹²⁵I-αBgtX binding to striatal extracts is indicated. C, IPP experiments were conducted on extracts from the dorsal striatum of α6+/+ mice after 6-OHDA lesions. Each value is the mean of two to three independent determinations on different groups of animals (^*p < 0.05 compared with saline-lesioned groups; Student's t test). The extent of DA denervation was assessed by ³H-WIN35,428 binding, a ligand for DA transporter (204 ± 26 and 41 ± 3 fmol/mg protein in the saline- and 6-OHDA-lesioned groups, respectively). D, α6^* and α4^* nAChRs were purified from α6+/+ striatal extracts using an anti-α6 and an anti-α4 affinity column. (nonα6)α4^* nAChRs were purified on an anti-α4 affinity column using striatal extracts from α6-/- mice or from α6+/+ mice after α6 depletion. The subunit content of purified nAChRs was determined by IPP. The amount of ³H-Epi immunoprecipitated is expressed as percentage of total ³H-Epi bound to the purified material before IPP (n = 3).