Experimental design for neuronal counting. 12 slides were utilized in these experiments, with 4 slides for each growth factor. The antibodies used on each slide are shown to the right of the slide along with the wavelength for the corresponding secondary antibody. For the 2 matching wells for each slide (growth factor concentration), the neuron numbers were averaged to give one observation (since the wells were not derived from independent cultures). Each slide contained a no growth factor control (blue), hence n = 9 for this condition. All other growth factors at 1 (i.e. NGF, red), 10 (i.e. GDNF, green) or 100 ng/ml (i.e. BDNF, yellow) are n = 3. The same slides were then utilized to ascertain the proportions of neurons expressing CGRP- or TRPV1-immunoreactivity or IB4-binding, as described in Methods. This figure refers to Figures 2 and 3 and Table 1.