Fig. 3. Purified Bdnf^–/– granule cells have a decreased migratory index. Freshly isolated wild-type and Bdnf^–/– granule cells were plated on previously established wild-type and Bdnf^–/– glial cultures, respectively. After 1 day in vitro, attachment and migration were analyzed by time-lapse video microscopy. One frame every 3 minutes was recorded for 90 minutes. (A) The same proportion of wild-type (230 of 1508) and Bdnf^–/– (205 of 1280) granule cells attached to glial processes. (B) The proportion of attached Bdnf^–/– (36 of 205) granule cells that migrated along glial fibers (the migratory index) was significantly lower than that for wild-type (96 of 230) granule cells. *P<0.0001 by ² analysis. (C) Once moving, the migratory rate was the same in wild-type and Bdnf^–/– cells. White bars, wild-type animals; black bars, Bdnf^–/– littermates.