Selectivity of rabbit polyclonal antibodies raised against splice variants of the NR1 subunit of the NMDA receptor. Antibodies were raised against synthetic peptides and used for western blots. The peptide sequences used to raise the antibodies were SKKRNYENLDQLSYDNKRGPC, DRKSGRAEPDPKKKATFRAC, PRRAIEREEGQLQLC, and QYHPTDITGPLNLSDPS for exons 5 (N1), 21 (C1), 22 (C2) and 22 minus (C2') respectively. The antibodies were purified with affinity columns and tested against cloned splice variants of the NR1 subunit transfected into COS-7 cells. The three numbers at the top of the columns identify the splice variant clones. The first number indicates the presence (1) or absence (0) of N1, the second C1 and the third C2. The protein was compared to protein taken from non-transfected cells and rat brain homogenates.