Fig. 5. BDNF is acutely motogenic for granule cells. Freshly isolated Bdnf^–/– granule cells were plated on previously established Bdnf^–/– glial cultures. After 1 day in vitro without added BDNF, attachment and migration were analyzed by time-lapse video microscopy for 90 minutes (pre addition). BDNF (10 ng/ml) or vehicle control was then added to the medium and migration of the same cells was followed for a second 90 minute period (post addition). (A) An individual Bdnf^–/– granule cell was followed over time. The granule cell (arrow) remains stationary until BDNF is added then rapidly began to migrate along the glial cell. Arrow indicates the migrating granule cell, arrowhead indicates a fixed position within the images. (B) Cumulative data show that BDNF, but not vehicle control, increased the migratory index of granule cells and thus is acutely motogenic. We monitored the acute response of 212 cells to BDNF and 100 cells to vehicle control. **P<0.0006 by ² analysis.