Localization of Ptc1 (A,D), Gli1 (B, E), and PAC1 (C, F) gene expression in postnatal day 1 rat brain by in situ hybridization. Dark-field photomicrographs of sagittal sections of cerebellum are shown in A–C (scale bar, 500 μm). Bright-field views of corresponding boxes at higher magnification are shown in D–F (scale bar, 50 μm). PL, Purkinje cell layer; SC, spinal cord.