Regulation of the development of locus coeruleus neurons in vitro.

Primary dissociated cultures of embryonic locus coeruleus (LC) neurons were established. Norepinephrine (NE) uptake was used as an index of maturation of the noradrenergic (NA) neurons from the LC. When LC cells were cocultured with a low density of hippocampal target cells, NE uptake was stimulated. However, increasing the concentration of hippocampal cells resulted in a significant decrease in NE uptake. The target stimulatory effect was mediated by both neurons and glia, whereas the inhibitory effect was mediated by direct contact between target glia and LC neurons and detected only in the presence of serum. In addition to the effect of target, we also tested the effect of elevated intracellular cAMP levels on NE uptake versus GABA uptake. GABA uptake was an index of development of non-NA cells. Increasing intracellular cAMP resulted in selective stimulation of NE uptake. These studies illustrate the potential of dissociated LC cultures in studying the regulation of NA axonal outgrowth.