CONTROLLED TARGETING OF TYROSINE-HYDROXYLASE PROTEIN TOWARD PROCESSESOF LOCUS-COERULEUS NEURONS DURING POSTNATAL-DEVELOPMENT

Dendrites of locus coeruleus (LC) neurons laying within the pericoerul ean neuropil (PCA) organize the major site where tyrosine hydroxylase (TH) is present throughout postnatal development. Those dendrites cons titute the neuronal compartment in which TH levels increase beyond pos tnatal day (P) 21 or after RU24722-induced TH expression. Distal LC de ndrites are present in the PCA by at least P20 but are devoid of TH an d can rapidly accumulate TH protein when gene induction is triggered. Contrasting with the increase in TH levels within LC perikarya and den drites, TH-mRNA concentration remains constant in LC perikarya from P4 to P42. Thus, supposing TH synthesis and degradation are also constan t, any change in TH levels targeted toward axons might be balanced by a shift in the TH deposition within LC dendrites. This mechanism may b e crucial in functions that the different processes of LC neurons have at critical steps of postnatal ontogeny. (C) 1997 Elsevier Science B. V.