QUANTITATIVE-ANALYSIS OF LONG-TERM SURVIVAL AND NEURITOGENESIS IN-VITRO - COCHLEOVESTIBULAR GANGLION OF THE CHICK-EMBRYO IN BDNF, NT-3, NT-4 5, AND INSULIN/

The dynamics of survival and growth were examined for cochleovestibula r ganglion (CVG) cells maintained in long-term cultures. CVG cells wer e explanted from chick embryos after 90 h of incubation into a defined -medium containing BDNF, NT-3, or NT-4/5 and an insulin, transferrin, selenium, and progesterone supplement. Explant survival and neuritogen esis was measured for 23 to 24 days in vitro. All three neurotrophins prolonged CVG survival in a dose-dependent manner although insulin act ed as a cofactor. In 0.872 mu M insulin-containing medium the ED50 for BDNF and NT-3 was 100 pg/ml, whereas the ED50 for NT-4/5 was 600-1200 pg/ml. However, at later ages in vitro, survival decreased with conce ntrations of BDNF greater than 2 ng/ml. In insulin-free medium, concen trations of 5-200 ng/ml of BDNF or 30-200 ng/ml of NT-4/5 maintained t he survival of explants at a rate that was equivalent to or less than the survival rate of cultures treated with insulin but not with neurot rophin. In contrast, NT-3-treated explants in insulin-free medium did not survive the duration of the experiment. Dose-dependent effects of BDNF and NT-3 on explant neuritogenesis were reflected as an initial d elay in outgrowth, whereas NT-4/5 had no effect. Insulin regulation of neuritogenesis was suggested when outgrowth decreased in the presence of an antibody to the insulin receptor. These data suggest that while all three of these neurotrophins protect the CVG from death the long- term consequences of cofactors and certain dose levels should be consi dered when treating CVG cells in vivo. (C) 1997 Academic Press.