BMP-5 promotes dendritic growth in cultured sympathetic neurons. Non-neuronal cells were eliminated from SCG cultures by treatment with anti-mitotic agent during the 2nd and 3rd days in vitro. Beginning on day 5, sympathetic neurons were treated with either control medium (A), medium supplemented with 50 ng/ml BMP-7 (B), or medium containing 300 ng/ml BMP-5 (C). Six days later, cultures were immunostained with mAb against MAP2, a protein found primarily in dendrites and neuronal somata. Neurons grown under control conditions lack dendrites (A). In contrast, neurons exposed to BMP-7 (B) or BMP-5 (C) typically have several tapered dendrites. Bar, 50 μm.