Journal of Neuroscience, Vol 7, 2352-2363, Copyright © 1987 by Society for Neuroscience
The coexistence of serotonin- and substance P-like immunoreactivity in the spinal cord of the rat as shown by immunofluorescent double labeling
MW Wessendorf and R Elde
This study surveyed the coexistence of serotonin-like immunoreactivity
(5-HT-IR) with substance P-like immunoreactivity (SP-IR) in fibers and
terminals within various portions of the spinal cord of the rat. A
previously characterized technique of immunofluorescent double labeling was
used to stain 5-HT-IR red and SP-IR green, and a search was then made for
single fibers that fluoresced both colors. These were found to be most
common in the ventral horn, wherein 99% of 5-HT-IR fibers were also
immunoreactive for SP. Coexistence of these substances was very rare in the
superficial dorsal horn: fewer than 3% of 5-HT-IR fibers were
immunoreactive for SP. In the region surrounding the central canal and in
the intermediolateral cell column (IML), over half of all 5-HT- IR fibers
and terminals were doubly labeled. In the white matter, doubly labeled
fibers were most common in the ventral funiculus and somewhat less common
in the lateral funiculus. They were rare in the dorsal columns. It is
concluded that the coexistence of 5-HT and SP in nerve fibers and terminals
is associated with somatic and sympathetic autonomic motoneurons. The role
of the coexistence of 5-HT and SP in somatosensation, including pain, is
unclear.