BEAT KNPSEL*t, JOHN W. WINSLOWt, ARNON ROSENTHALt, Louis E. BURTONt, DERICE P. SEID*,

Recombinant human brain-derived neuro- trophic factor (rhBDNF) and neurotrophin 3 (rhNT-3), two recently cloned molecules closely related to nerve growth factor (NGF), were produced from human cDNA expressed in human embryonic kidney cells. The recombinant proteins were tested in cultures of dissociated fetal rat brain cells containing basal forebrain cholinergic neurons. rhBDNE stimulated the differ- entiation of the cholinergic neurons, similar to NGF, which is well established as a neurotrophic factor for these cells. How- ever, rhBDNF was particularly effective during the first few days in vitro, whereas the stimulatory action of rhNGF was more pronounced later in the development of the cultures. This finding indicates the existence of different time periods of responsiveness of the cholinergic neurons to BDNF and NGF. To assess the selectivity of the effect of rhBDNF on cholinergic neurons, its actions were tested in cultures of ventral mesen- cephalon containing dopaminergic cells. In contrast to NGF, which does not affect central dopaminergic neurons, rhBDNF increased dopamine uptake activity. The findings suggest that BDNF stimulates survival or differentiation of other cells besides the cholinergic neurons.