BMP-5 induces phosphorylation of Smad-1 in cultured sympathetic neurons. (A) Blots of cell lysates from SCG cultures consisting solely of neuronal cells were probed using Ab that specifically recognizes the phosphorylated form of Smad-1. Under control conditions (time = 0 min), phosphorylated Smad-1 is not detected. Treatment with BMP-5 (100 ng/ml) causes a time-dependent increase in the band density of phosphorylated Smad-1. (B) Densitometric analyses of Western blots of cell lysates from purified neuronal cell cultures at varying times after exposure to BMP-5. Equal amounts of protein were loaded into all wells and each blot was probed initially for p-Smad, then stripped and successively probed for total Smad and tubulin. Data are presented as the mean ± S.E.M. (n = 2 per experimental condition).