Rat sympathetic neurons express β-galactosidase and EGFP genes transfected using PEI. (A) and (B) show a transfected neuron stained with X-gal 10 d after introduction of plasmid taken at low and high magnification, respectively. In (A), note the extensive spread of β-galactosidase throughout the neuronal processes, including growth cones. In (B), note the non-transfected cell immediately adjacent to the soma of the β-gal+ neuron (arrow). (C) shows a neuron stained with a monoclonal antibody to β-galactosidase next to two nontransfected cells (arrows). An EGFP+ neuron is shown in (D). Note the distribution of EGFP throughout the neurites in (D). Scale bar = 80 μm in (A), 20 m in (B), 40 μm in (C) and (D).