BDNF stimulated outgrowth is Ca²⁺ dependent and requires Ca²⁺ release from internal stores.

(A) Bath application of BDNF elicits a strong Ca²⁺ signal in zebrafish growth cones (pseudocolored according to scale on left, with blue  =  lower [Ca²⁺] and white  =  higher [Ca²⁺]), quantified in (B). Treatment with both (C) BAPTA-AM, a cytoplasmic Ca²⁺ buffer, and (D) thapsigargin, which depletes intracellular Ca²⁺ pools, abolish BDNF stimulated outgrowth. Scale bar, 5 µm. *, p<0.05; ns, not significant.