Fig. 7. Delayed administration of NT4 for 24 hours but not 48 hours increases the number of TH-positive cells in LCr cultures. NT4 was added to E13.5 LCr cultures at the time of plating or after 24 or 48 hours and then the cultures were fixed after 24, 48 or 72 hours. Counts of TH immunoreactive cells revealed that addition of NT4 after 24 hours gave the same number of TH-positive cells than at the time of plating, suggesting a second effect of NT4 distinct from the early survival-promoting effect. *P<0.01, unpaired t-test.