The relationship between PPD, nNOS, parvalbumin, NPY and galanin. Confocal scans from the superficial dorsal horn to show staining for PPD and four other compounds that have been detected in subsets of inhibitory interneurons: nNOS, parvalbumin (PV), NPY and galanin (Gal). In each case the image on the left shows PPD (magenta), the one in the middle shows the other compound (green), while the one on the right is a merged image. a-c: a scan through lamina I and the outer part of lamina II shows a PPD-immunoreactive cell (arrow) close to 2 nNOS+ cells (arrowheads). d-f: a scan through the middle part of lamina II shows a PPD+ cell (arrow) and two parvalbumin cells (arrowheads). Note that the upper part of this field (lamina IIo) contains numerous PPD-immunoreactive profiles and little parvalbumin staining, while the lower part (lamina IIi) has many parvalbumin-containing structures, and relatively few that are PPD+. g-i: a field from lamina II that contains two PPD cells (arrows) and two NPY cells (arrowheads). Note the lack of co-localisation of PPD with nNOS, parvalbumin or NPY in these images. j-l: a scan through laminae I and IIo shows 3 PPD cells. Two of these (arrowheads) are also galanin-immunoreactive, while the other one (arrow) is not. Images were obtained from 3 (a-f) or 4 (g-l) confocal images at 0.5 μm z-spacing. Scale bar = 20 μm.