Immunocytochemical experiments with fluorescent secondary antibodies. The insets in A – C show higher magnifications of the apical and inset D the basal epithelia. A Gαolf labels a thick fringe of olfactory cilia in zone 5 (caudal turbinate). B In zone 2 (anterior nasal cavity) considerably fewer cilia are Gαolf-positive. C The YOL 1/34 antibody, a marker for microtubules, shows a fair amount of olfactory cilia in zone 3 (between the anterior turbinate and the anterior nasal cavity). D Substance P-positive fibers are present beneath the olfactory epithelium in zone 1 (most anterior nasal cavity). Some fibers reach into the epithelium where they may innervate SCCs.