Odorants induce MAPK and CREB phosphorylation in the olfactory epithelium. (A) Cryosections (12 μm) of mice expressing GFP in every mature OSN (OMP-GFP) were subjected to immunohistochemistry using an antibody specific for phosphorylated p42/44 MAPK in the olfactory epithelium. After 2 hours of odorant exposure a strong anti-phospho-p42/44 MAPK immunoreactivity was observed in the cytoplasm of OSNs. (B) Staining for phospho-CREB (Ser-133). Phospho-CREB was observed in the sustentacular cell layer, in the nuclei of OSNs, and in immature OSNs not expressing OMP, after exposure to a mixture of 100 different odorants for 2 h. Control panel with secondary antibody only or after using a specific blocking peptide shows very low background labeling intensity in the nuclei of the different cell types. (C) WB analysis of control cell lysates (SK-N-MC cells prepared with IBMX and forskolin treatment) and olfactory epithelium samples with CREB and phospho-CREB (Ser-133) specific antibodies showing labeling of the proteins (bands marked by stars), which is abolished when the specific blocking peptide was pre-incubated with the antibody.