Localization of NADPH diaphorase in the thoracolumbar and sacrococcygeal spinal cord of the dog.
The distribution of NADPH-d activity and NOS-immunoreactivity in the spinal cord of the dog was studied to evaluate the role of nitric oxide in lumbosacral afferent and spinal autonomic pathways. At all levels of the spinal cord examined, NADPH-d staining and NOS-immunoreactivity were present in neurons and fibers in the superficial dorsal horn, dorsal commissure and in neurons around the central canal. Sympathetic preganglionic neurons in the rostral lumbar segments identified by choline acetyl transferase (ChAT) immunoreactivity exhibited prominent NADPH-d and and NOS-immunoreactive staining; whereas the ChAT-immunoreactive parasympathetic preganglionic neurons in the sacral segments were not stained. The most prominent NADPH-d activity in the sacral segments occurred in fibers extending form Lissauer's tract through lamina I along the lateral edge of the dorsal horn to the region of the sacral parasympathetic nucleus. These fibers were prominent in the S1-S3 segments but not in adjacent segments (L5-L7 and Cx1 or in thoracolumbar segments. The NADPH-d fibers were not NOS-immunoreactive, but did overlap with a prominent fiber bundle containing vasoactive intestinal polypeptide immunoreactivity in the sacral spinal cord. These results indicate that nitric oxide may function as a transmitter in thoracolumbar sympathetic preganglionic neurons, but not in sacral parasympathetic preganglionic neurons. The functional significance of the NADPH-d positive, NOS-negative fiber bundle on the lateral edge of the sacral dorsal horn remains to be determined. However, based on anatomical studies in other species it seems reasonable to speculate that the fiber tract represents, in part, visceral afferent projections to the sacral parasympathetic nucleus.
Vizzard
M A
MA
Department of Neurology, College of Medicine, University of Vermont, Burlington 05405, USA.
Erickson
K
K
de Groat
W C
WC
D000818:Animals; D004285:Dogs; D008161:Lumbosacral Region; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D009412:Nerve Fibers / Q000201:enzymology; D009474:Neurons / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D012445:Sacrococcygeal Region; D013116:Spinal Cord / Q000166:cytology / Q000201:enzymology*; D013909:Thorax; D014018:Tissue Distribution; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D014660:Vasoactive Intestinal Peptide; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase