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

Abstract

The existence of noradrenergic projections from the lateral reticular nucleus (LRt) to the dorsal quadrant of cervical, thoracic, or lumbar spinal cord was investigated using a combined method of WGA-apo-HRP-gold retrograde tracing and dopamine-beta-hydroxylase (DBH) immunocytochemistry. Preliminary retrograde tracing studies indicated that LRt neurons projecting to cervical, thoracic, or lumbar spinal cord were characteristically located near the perimeter of the LRt. Double-labeling experiments demonstrated that a portion of these peripherally-located, spinal-projecting neurons were DBH-immunoreactive. Double-labeled neurons were also located at the parvocellular division of the contralateral LRt in the thoracic injection cases. Double-labeled neurons were not observed at the subtrigeminal division in cervical, thoracic, or lumbar injection case. The results suggest the possibility that the noradrenergic LRt-spinal pathway might be involved in a variety of pain processing and cardiovascular regulatory functions in the rat.

Neurokinin-1 Projection Cells in the Rat Dorsal Horn Receive Synaptic Contacts from Axons That Possess α2C-Adrenergic Receptors

“…These lines of evidence suggest that NK-1 neurons are likely to be components of the circuitry that underlies NE antinociception. NE descending inhibitory systems could be recruited by NK-1 spinomedullary neurons, because these cells terminate in a region close to the lateral reticular nucleus that contains dopamine ␤-hydroxylaseimmunoreactive neurons, which in turn, project to the spinal dorsal horn (Lee et al, 2001).…”

Evidence That Adrenergic Ventrolateral Medullary Cells Are Activated whereas Precerebellar Lateral Reticular Nucleus Neurons Are Suppressed during REM Sleep

“…At relatively rostral levels, there are the adrenergic cells of the C1 group, many of which drive the sympathetic output and have extensive connections within the brainstem [42], [43], [44], [45], [46], [47], [48], [49], [50]. Further caudal, the VLM contains noradrenergic cells (A1 group) that may contribute to cardiovascular and pain regulations [51], [52], [53], [54], [55] through their axonal projections to the brainstem and spinal cord [56], [57]. They mainly aggregate just dorsal and dorsomedial to the lateral reticular nucleus (LRN), a major precerebellar structure that integrates descending motor commands with vestibular information and flexor reflex afferents ascending from the spinal cord [58], [59], [60], [61], [62], [63], [64].…”

Pain Modulation from the Locus Coeruleus in a Model of Hydrocephalus: Searching for Oxidative Stress-Induced Noradrenergic Neuroprotection

“…An increase in both TH and DBH-IR fibers was detected in the spinal dorsal horn of hydrocephalic rats. Although the expression of those cathecolamine-synthetizing enzymes is frequently used in studies to indicate NA expression [ 40 , 41 , 42 , 43 , 44 ], it is important to perform direct NA measurements at the spinal cord. Noradrenergic innervation of the spinal dorsal horn in the rat strain used in the present study mainly originated from the LC, since around 85% of all noradrenergic neurons projecting to the spinal dorsal horn are located at the LC.…”