Journal of Neuroscience, Vol 4, 757-766, Copyright © 1984 by Society for Neuroscience
Non-serotonergic origins of the dorsolateral funiculus in the rat ventral medulla
JN Johannessen, LR Watkins and DJ Mayer
Cells within the ventral medulla whose axons descend to the spinal dorsal
horn via the dorsolateral funiculus (DLF) play an important role in pain
modulation. Previous evidence suggests that this pathway is primarily
serotonergic. We have examined this hypothesis directly using combined
retrograde horseradish peroxidase/serotonin immunohistochemical staining.
Cells of the ventral medulla contributing to the DLF were found to be
largely non-serotonergic. This result was confirmed by two approaches: by
the absence of a significant number of double-labeled cells following
discrete horseradish peroxidase labeling of the DLF and by the persistence
of double-labeled cells in animals with DLF lesions made rostral to
intraspinal injections of horseradish peroxidase solutions. The conclusion
is made that the previously described nucleus raphe magnus-DLF-dorsal horn
pathway is predominantly non-serotonergic.