The expression of the vesicular monoamine transporter was studied in newborn rat sympathetic neurons and compared to that of the catecholamine biosynthesis enzymes tyrosine hydroxylase and dopamine-beta-hydroxylase. The vesicular monoamine transporter was assayed using the specific ligand [3H]dihydrotetrabenazine. In cultures grown for 10 days in the presence of 35 mM K+, tyrosine hydroxylase activity and the density of [3H]dihydrotetrabenazine binding sites were increased by a similar 2-3-fold factor, while dopamine-beta-hydroxylase activity and protein level were unchanged. Under these conditions, choline acetyltransferase activity was depressed by 90%. The induction of the vesicular monoamine transporter by high K+ was dependent upon Ca2+ entry through slow calcium channels since it was inhibited by the diphenylbutylpiperidine antagonist fluspirilene and by 20 mM Mg2+, and was enhanced by the dihydropyridine agonist, Bay K8644. The induction of the vesicular monoamine transporter by neuronal depolarization indicates the existence of a Ca2(+)-dependent mechanism of coregulation for this intrinsic component of monoaminergic synaptic vesicles and tyrosine hydroxylase. On the other hand, the apparent absence of dopamine-beta-hydroxylase induction is probably due to the continuous secretion of this intravesicular enzyme by the depolarized sympathetic neurons, an effect already observed in trans-synaptically stimulated adult sympathetic ganglion and adrenal medulla.