Postnatal development of dopamine-beta-hydroxylase-immunoreactive fibers of the spinal cord of the rat.

The development of dopamine-beta-hydroxylase (DBH)-immunoreactive fibers of the rat spinal cord was studied in the cervical, thoracic and lumbar regions at birth, 6, 14, 30 and 90 days of age. The adult pattern of distribution of DBH-immunoreactive fibers is similar to that of catecholaminergic histofluorescence. Our results suggest that DBH immunoreactivity is more sensitive than glyoxylic acid methods in early development, since the immunocytochemical method demonstrates stained fibers at an earlier age than the histofluorescence method. At birth noradrenergic innervation was already established; DBH immunoreactivity was notable in the ventral horn of the lumbar region and in the zona intermedia (ZI); the new finding was that not only the intermediolateral cell column but also the dorsal autonomic nucleus and the transverse connections between them were distinctly stained and were periodically organized. With increasing age, the general rule is that the intensity of the staining increased simultaneously in all regions. In the gray matter, networks of stained fibers became more complex. In contrast to earlier workers, we found no evidence for 'selective destruction' of noradrenergic fibers within the ZI in the postnatal period. The exceptions to the rule are DBH-immunoreactive fibers in the ventral white matter; these fibers increased in number up to day 14 and appeared to decrease thereafter; they were most numerous in the cervical region and diminished in number caudally; these fibers were diffuse in the cervical region but as they coursed caudally they became concentrated in a more ventral marginal location.