Complete series through the brains of 4 CRFR1-GFP mice were prepared for concurrent localization of GFP and CRFR1 mRNA. Combining immunoperoxidase labeling with isotopic in situ hybridization required minor modifications of the constituent methods (Chan et al., 1993 (link)). Immunostaining was carried out first, and the protocols modified as follows: (1) normal tissue pretreatments in hydrogen peroxide and sodium borohydride were omitted, (2) blocking sera were replaced in the immunostaining procedure with 2% bovine serum albumin and 2% heparin sulfate, (3) nickel enhancement steps were eliminated, and (4) Nissl counterstaining was omitted.