Fig. 4. Representative fluorescence photomicrographs of rainbow trout PCV cross-sections demonstrating (A) the presence of eNOS immuno-positive cells (red) in close proximity to the chromaffin cells (green) as identified by aldehyde-induced fluorescence. Cell nuclei are indicated by blue fluorescence (DAPI staining). (B) A representative western blot of trout PCV tissue demonstrating the presence of a single immunoreactive band at approximately 140 kDa (lane 1) that was absent after preabsorption of the eNOS antibody with blocking peptide (lane 2). There was no detectable red or green fluorescence in sections not treated with aldehyde and on which the primary antibody was omitted (C).