Fig. 2. Immunohistochemical analysis of neural cell proliferation in the olfactory mucosa indicates that it is higher in young mice than in adults. Proliferating cells in the OE were detected using an antibody either against BrdUrd or against PCNA, a marker of proliferating cells. Arrowhead, the basal lamina lining the OE in the olfactory mucosa; arrow, some labeled cells; nc, nasal cavity; ch, chorion; bc, basal cell(s); on, olfactory neuron(s); scale bar, 100 µm. The number of dividing cells are reduced in the OE of 3-month-old mice by comparison with that of 3-week-old mice (see also Table 1 ).