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. 1999 Jul 1;19(13):5393–5408. doi: 10.1523/JNEUROSCI.19-13-05393.1999

Fig. 5.

Fig. 5.

Analysis of neurite outgrowth in response to NGF or NGF plus BDNF in p75NTR−/− versus p75NTR+/+ sympathetic neurons. A, B, Results of colorimetric MTT assays to measure mitochondrial function and survival of murine sympathetic neurons in response to NGF or NGF plus BDNF. A, Neonatal murine sympathetic neurons were cultured in 50 ng/ml NGF for 5 d, washed free of neurotrophin-containing medium, and switched for 2 d to various concentrations of NGF as indicated on the x-axis. Results from one representative experiment performed in triplicate are shown. In these assays, absolute values are normalized so that the value obtained with 0 neurotrophin is 0% survival, whereas that obtained with 10 ng/ml NGF is considered 100% survival. Error bars represent SEM. Note that 5 ng/ml NGF is capable of eliciting maximal survival of murine sympathetic neurons. B, Neonatal murine sympathetic neurons were cultured as in A and were then switched into various concentrations of NGF plus 100 ng/ml BDNF, as denoted on the x-axis. These data represent values from one representative experiment performed in triplicate. Values are normalized as in A; error bars represent SEM. As with rat sympathetic neurons, BDNF does not affect survival in optimal concentrations of NGF. C, D, Quantitative analysis of neuritic process density in p75NTR−/−versus wild-type murine sympathetic neurons in response to NGF or NGF plus BDNF. In the two separate experiments shown here, p75NTR−/− versus wild-type neonatal sympathetic neurons were cultured as sister cultures for 3 d in 50 ng/ml NGF and were then switched for an additional 2 d to 7.5 ng/ml NGF plus or minus 100 ng/ml BDNF. * denotes values that were significantly different in the comparison between NGF versus NGF plus BDNF (*p < 0.05); ** denotes those values that were significantly different in the comparison between p75NTR−/− versus wild-type (WT) neurons in response to 7.5 ng/ml NGF (**p < 0.05). Note that p75NTR−/− neurons grow more robustly than wild-type neurons in response to the same concentration of NGF. Note also that BDNF significantly reduces the NGF-mediated growth of wild-type (p < 0.05) but not p75NTR−/− (in both experiments,p > 0.38) neurons. D, The experiments shown in C were normalized so that the neuritic density of wild-type neurons at 10 ng/ml NGF was 100 and then averaged to provide an index of the relative neurite density.