Fig. 7.

GDNF is the exclusive physiological ligand for GFRα-1 in P1 MNs in slice culture. A, Slices were cultured for 6 d in the presence of 200 ng/ml GDNF, NRTN, ARTN, or PSPN. The mean ± SEM of three to five independent experiments for each condition is shown. B, In a separate experiment, a combination of NRTN and ARTN did not increase MN survival over baseline. The addition of NRTN, ARTN, and PSPN to GDNF did not significantly change the survival response to GDNF alone. C, Slice cultures prepared from mice null for GFRα-1 and wild-type littermates were treated with GDNF alone. GDNF survival signaling was completely abolished in GFRα-1^−/− MNs. ***p < 0.001.