Effects of intraplantar POMC-MIDGE-NLS on β-endorphin expression in paws. β-galactosidase (β-GAL)-MIDGE-NLS, POMC-MIDGE-NLS or control MIDGE-NLS (each at 50 μg) were injected into both hindpaws at 4 days after induction of inflammation. Staining was performed 24 h later. Positive staining for β-GAL (in blue), particularly visible in inflamed paws, indicates that MIDGE vectors can transfect cells (some marked with black arrows) in vivo. β-endorphin (END; brown staining) is expressed in immune cells after treatment with POMC-MIDGE-NLS or control MIDGE-NLS. Morphologically these cells appear as polymorphonuclear (red arrows) and mononuclear cells (red stars), shown in the dash-boxed inserts at a higher magnification of the respective solid line boxes. Bars = 20 μm.