Neuroblast cell death in ovo and in culture: interaction of ethanol and neurotrophic factors.

We used two experimental paradigms to examine the influence of the neurotrophins, NGF, EGF, and bFGF on normal neuroblast survival and also after ethanol insult. In the first paradigm, chick embryos received in ovo at embryonic day 1 and 2 (E1 and E2) saline (control) ethanol (10mg/50 microliters/day), NGF (50 ng/50 microliters/day), or EGF (25 ng/50 microliters/day), or ethanol+NGF or EGF. At E3, cultures were prepared from whole embryos separately from each group. At C2, all cultures were labeled with [3H]thymidine and assessed for effects or neuronal survival. In the second paradigm, cultures were prepared from 3-day-old whole embryos and at C0, cultures were treated with either ethanol (50 mM) alone, NGF (50 ng/ml) alone, EGF (25 ng/ml) alone, bFGF (50 ng/ml) alone, or were treated concomitantly with ethanol plus one of the neurotrophins; control had only the culture medium, DMEM + 5% FBS. We obtained the following findings. 1) Cultures derived from embryos treated with either of the three neurotrophins exhibited a higher neuronal survival as compared to controls (1st paradigm). 2) The survival-promoting effect was also observed when the neurotrophins were added directly to the cultures (2nd paradigm). 3) As reported previously, cultures derived from ethanol-treated embryos exhibited a marked decline in neuronal survival as compared to controls. 4) All three neurotrophins attenuated the decline in neuronal survival produced by ethanol. The 'rescuing' effects of the neurotrophins support our early hypothesis that ethanol administration during early neurogenesis interferes with microenvironmental trophic signals essential for neuroblast survival and differentiation.