Evidence that dopamine-beta-hydroxylase immunoreactive neurons in the lateral reticular nucleus project to the spinal cord in the rat

The existence of noradrenergic projections from the lateral reticular nucle us (LRt) to the dorsal quadrant of cervical, thoracic, or lumbar spinal cor d was investigated using a combined method of WGA-apo-HRP-gold retrograde t racing and dopamine-beta-hydroxylase (DBH) immunocytochemistry. Preliminary retrograde tracing studies indicated that LRt neurons projecting to cervic al, thoracic, or lumbar spinal cord were characteristically located near th e perimeter of the LRt. Double-labeling experiments demonstrated that a por tion of these peripherally-located, spinal-projecting neurons were DBH-immu noreactive. Double-labeled neurons were also located at the parvocellular d ivision of the contralateral LRt in the thoracic injection cases. Double-la beled neurons were not observed at the subtrigeminal division in cervical, thoracic, or lumbar injection case. The results suggest the possibility tha t the noradrenergic LRt-spinal pathway might be involved in a variety of pa in processing and cardiovascular regulatory functions in the rat. Anat Rec 263:269-279, 2001. (C) 2001 Wiley-Liss, Inc.