Biochemical characterization of [3H]norepinephrine uptake in dissociated brain cell cultures from chick embryos

The uptake of ³H]norepinephrine (³H]NE) was studied in dissociated brain cell cultures prepared from 8-day-old chick embryos using the whole brain (minus optic lobes). Uptake of ³H]NE, 5×10^–9 M, 10 min incubation, in freshly dissociated noncultured embryonic chick brain cells, was detected in 6-day-old embryos; it was temperature and drug (cocaine, metanephrine) sensitive and increased with brain development. In cultured cells, which were assayed at various days in culture, the increase in ³H]NE accumulation per culture was less than that seen in freshly dissociated noncultured embryonic cells. When ³H]NE uptake was expressed per mg protein, a decrease with days in culture was observed, reflecting perhaps a dilution of growth or proliferation of cells not accumulating NE. Metanephrine, 5×10^–6 M, an inhibitor of extraneuronal uptake, inhibited ³H]NE in 5-day-old cultures whereas desmethylimipramine, an inhibitor of neuronal uptake, inhibited ³H]NE uptake in 15- and 20-day-old cultures. Cocaine, another neuronal inhibitor, inhibited ³H]NE at 10 and 15 days only. We interpret these findings to suggest that during early growth in culture most neuroblasts accumulate NE nonspecifically and, as neuronal maturation proceeds, NE accumulation becomes specific.