Figure 6.

Conditions that promote NM synthesis delay neurite outgrowth. Cells were scored as displaying processes if they exhibited a neurite that extended at least one cell body length. Cells were exposed to 100 μM d-DOPA for 30 days, with replacement of medium containing the compound in 2- to 3-day intervals. After two additional replacements with medium without d-DOPA and subsequent washing, NGF (50 mg/ml) was added. The cells were scored at 1- to 2-day intervals for neurite outgrowth (n = 3 cultures, 100 cells scored per culture, ± SEM). Similar results were observed in five independent experiments and after similar l-DOPA exposure (not shown).