Many dopaminergic neurons in the mouse PG coexpress RET, the signaling component of the GDNF receptor. Photomicrographs show RET (A) and TH (B) immunostaining in the same tissue section through the PG of a wild-type E17.5 mouse embryo. Many TH-positive neurons are also RET-immunoreactive (large arrows). However, TH-positive/RET-negative (small arrows) and RET-positive/TH-negative (arrowheads) neurons were also observed. Approximately 43% of all dopaminergic neurons in the PG express RET (n = 5). RET immunoreactivity was also prominent in the E17.5 NG (C). Scale bar, 50 μm.