POSTNATAL-DEVELOPMENT OF ADRENERGIC TERMINALS IN RAT LOCUS-COERULEUS - WITH SPECIAL REFERENCE TO GROWTH OF NORADRENERGIC NEURONS

The postnatal development of noradrenergic (NA) neurons and adrenergic (AD) terminals in the rat locus coeruleus (LC) was studied immunohist ochemically. Cell body size was measured after staining of NA neurons with anti-tyrosine hydroxylase (TH) serum, and AD terminals were visua lized with anti-phenylethanolamine N-methyltransferase serum. NA neuro ns in the LC were strongly TH-immunoreactive throughout the postnatal period. At birth, their mean cell body volume was 660 +/- 30 mu m(3). It reached a maximum of 2580 +/- 230 mu m(3) at postnatal day (PD) 14, and decreased thereafter to 930 +/- 50 mu m(3) at PD 60. This transie nt enlargement of NA neurons may be closely related to the development of the cerebral cortex. AD afferents to the LC had terminals forming predominantly asymmetric junctions at birth (about 96% of all junction s). They occasionally made axo-somatic contact, suggesting that AD inp ut already modulated the activity of LC neurons at this stage. AD term inals making axo-spinous synapses increased in number until PD 31, but still represented a minor proportion of these LC terminals, since the re were more than 80% in contact with dendritic shafts at all ages exa mined.