Detectability of exogenous BDNF by standard ELISAversus ELISA in situ. BDNF (500 pg/ml) was added at plating to newborn NPG cultures (hatched gray bars) and to culture medium (Med.) alone (hatched white bars) and incubated for 72 hr in the absence (Standard ELISA) or presence of anti-BDNF monoclonal capture antibody (ELISA in situ). BDNF levels were also measured in control cultures (solid gray bars) to which exogenous BDNF was not added. ***p < 0.001; n.s., not significant.