The number of neurons that are positive only for p75 is increased in the ipsilateral side after axotomy. A, Confocal microscopy of double-immunofluorescence anti-ChAT/anti-p75 reveals an increase in the number of neurons that are positive only for p75 at different times after the axotomy. The superior panel is a panoramic view of the medial septum at 14 days after axotomy (scale bar: 1 mm). The central and inferior panels are magnification insets (scale bar: 200 μm) of neurons contralateral and ipsilateral to the lesioned side, showing p75-positive and ChAT-negative cells as indicated by the white arrows. B, The graph shows the percentage of total septal neurons expressing p75 that are p75-positive and ChAT-negative at 1, 3, 7 or 14 days after axotomy. Black bars represent the control side of the septum and white bars represent the side ipsilateral to the lesion. Asterisk indicates significance level p < 0.05.