We have previously reported that primary astrocyte cultures prepared from neonatal rat brains show Na(+)-dependent, tricyclic antidepressant-sensitive, high-affinity uptake of [3H]norepinephrine ([3H]NE). Other workers, however, using primary astrocyte cultures from neonatal mice, have failed to find such uptake. This prompted us to examine possible reasons for the variability of the uptake in primary astrocyte cultures such as growth conditions and the effect of ascorbic acid. The presence of ascorbic acid increased the Na(+)-dependent uptake of NE by inhibiting the Na(+)-independent component. Na(+)-dependent uptake in rat cultures occurs when either fetal bovine or horse serum are present in the growth media, but not in a serum-free growth medium. Other workers have shown a species difference such that, even under optimal uptake conditions where rat astrocyte cultures exhibit Na(+)-dependent [3H]NE uptake, mouse astrocyte cultures do not.