Figure 4

Co-immunostaining for keratin protein and nerve growth factor (NGF) in the hindpaw skin after intraplantar injection of substance P (SP). Keratin protein (green) and NGF (red) are shown in control rats (top row of panels), and at 1 h (second row), 3 h (third row), and 6 h (fourth row) after intraplantar injection of 25 μg SP. Increased NGF staining was observed in keratinocytes at 1, 3 and 6 h after SP injection, corresponding to the prolonged allodynia observed after SP injection (Figure 1). Scale bar = 40 μm.