Retrograde labeling of nodose neurons innervating the guinea pig trachea. (A) Low magnification of nodose ganglia showing individual (arrows) and clusters (circle) of fluorogold labeled nodose neurons that have not undergone subsequent secondary immunoprocessing (hence the neurons appear blue). (B) Higher magnification of two fluorogold-labeled nodose neurons that have undergone secondary immunoprocessing and relabeled with a rhodamine fluorophore (hence the neurons appear red). See methods for details. Scale bars represent 150 μm in A and 20 μm in B. (C) Histogram showing the distribution of retrogradely labeled nodose neurons based on somal perimeter. The superimposed line graph shows the moving average calculated from the histogram. See text for details.