Localization of noradrenergic terminals in sympathetic preganglionic nuclei of the rat: demonstration by immunocytochemical localization of dopamine-beta-hydroxylase.

The noradrenergic (NE) innervation to sympathetic preganglionic nuclei in the rat thoracic cord was studied by immunocytochemical localization of dopamine-beta-hydroxylase (DBH), a specific NE antigen. DBH antisera was prepared against DBH purified from bovine adrenal medulla. The most intense immunoreaction was observed within the intermediolateral cell column (IML) of the spinal cord, the major sympathetic preganglionic nucleus in mammals. DBH was also localized in both the central autonomic and intercalated nuclei, cell groups known to contain sympathetic preganglionic visceral motor neurons. Two weeks following a midthoracic spinal transection, DBH immunoreactivity was no longer observed caudal to the lesion. Thus, the cells of origin of these noradrenergic terminals are supraspinal. Following a midthoracic hemisection DBH, immunoreactivity was similarly reduced in both the ipsilateral and contralateral IML caudal to the lesion. Therefore, bulbospinal NE neurons project bilaterally to sympathetic preganglionic nuclei.