Figure 7.

BDNF-induced NGF release occurs independently of extracellular calcium, but requires mobilization of calcium from intracellular stores. (A) Cultured hippocampal neurons, which had been transduced with AdCMV-NGF, were perfused continuously. BDNF-induced secretion of NGF was unaffected by removal of extracellular calcium and the presence of BAPTA, but was fully abolished by intracellular chelation of calcium after loading of hippocampal neurons with BAPTA-AM. Standard errors are referred to four independent experiments. (B) BDNF mobilizes calcium from intracellular stores. Cultured hippocampal neurons were loaded with Fura-2/AM and the effect of bath application of 100 ng/ml BDNF on [Ca²⁺]_i was measured in the cell body. Graphs depict representative responses. In the absence of extracellular calcium a [Ca²⁺]_i elevation still was observed, albeit reduced, indicating that BDNF can mobilize calcium from intracellular stores. Intracellular chelation of calcium by previous loading of the neurons with BAPTA-AM abolished any change in the fluorescence ratio.