The origins of catecholaminergic innervation in the rostral ventromedial medulla oblongata of the rat

The localization of catecholaminergic neuronal cell bodies which project to the rostral ventromedial medulla oblongata (RVM) were investigated by the combined technique with dopamine beta-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT) or tyrosine hydroxylase (TH) immunocytochemistry and retrograde neuronal tracing method using fluorescent latex microspheres (FluoSpheres) injected into the center of the RVM, the nucleus raphe magnus (NRM). Noradrenaline (NA) neurons in Al, A5, A7 regions, locus coeruleus (LC) and nucleus subcoeruleus (SC) and adrenaline (Ad) neurons in Cl region were double-labeled due to DBH or PNMT and retrogradely transported FluoSpheres, and the ratio of their coexistence was higher in Al, A5, A7 and Cl than in LC and SC. No dopamine neurons in the midbrain and forebrain were double-labeled with TH and FluoSpheres. Thus, it was clarified that the RVM is innervated by the ventral groups of lateral tegmental NA and Ad neurons in the brainstem.