Immunohistochemical, Histochemical and Radioassay Analysis of Nitric Oxide Synthase Immunoreactivity in the Lumbar and Sacral Dorsal Root Ganglia of the Dog |
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Authors: | Nadežda Lukáčová Dalibor Kolesár Martin Maršala Jozef Maršala |
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Institution: | (1) Slovak Academy of Sciences, Institute of Neurobiology, Košice, Slovak Republic;(2) Anesthesiology Research Laboratory, University of California, San Diego, La Jolla CA, USA;(3) Slovak Academy of Sciences, Institute of Neurobiology, Šoltésovej 4, 040 01 Košice, Slovak Republic |
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Abstract: | Summary In this study, immunohistochemistry for neuronal nitric oxide synthase (bNOS-IR), nicotinamide adenine dinucleotide phosphate
diaphorase histochemistry (NADPHd) and nitric oxide synthase radioassay were used to study the occurrence, number and distribution
pattern of nitric oxide synthesizing neurons in the lumbar (L1–L7) and sacral (S1–S3) dorsal root ganglia of the dog. Nitric
oxide synthase immunolabelling was present in a large number of small- (area <1000 μm2) and medium-sized (area 1000–2000 μm2) as well as in a limited number of large-sized (area >2000 μm2) neurons. Although neuronal nitric oxide synthase immunolabelling and histochemical staining provided intense staining of
multiple small- and medium-sized neurons in all lumbar and sacral dorsal root ganglia, immunolabelled or histochemically stained
somata exhibited little topographic distribution in individual dorsal root ganglia. Great heterogeneity was noticed in the
immunolabelling of medium-sized nitric oxide synthase immunopositive neurons ranging from lightly immunolabelled somata to
heavily immunoreactive ones with completely obscured nuclei. Both staining procedures proved to be highly effective in visualizing
intraganglionic fibers of various diameters. In general, the largest fibers revealed at the peripheral end of lumbar and sacral
dorsal root ganglia were larger, 6.49–9.35 μm in diameter, while those running centrally and proceeding into the dorsal roots
were about 30% reduced, ranging between 5.32 and 8.67 μm in diameter. Peripherally, the occurrence of nitric oxide synthase
detected in axonal profiles, and confirmed histochemically, in the specimens of the femoral and sciatic nerves, is the first
indication of the presence of nitric oxide synthase in the peripheral processes of somata located in L4–S2 dorsal root ganglia.
Large and thin central nitric oxide synthase immunoreactive processes of L1–S3 dorsal root ganglion neurons segregate shortly
before entering the spinal cord, the former making a massive medial bundle in the dorsal root accompanied by a slim lateral
bundle penetrating Lissauer's tract. Quantitative assessment of the distribution of bNOS-IR and/or NADPHd-stained neurons
showed a peculiar pattern in relation to spinal levels. Apparent incongruity was found in the total number of NADPHd-stained
versus bNOS-IR neurons, demonstrating a clear prevalence of small bNOS-IR somata in all lumbar ganglia, while medium-sized
NADPHd-stained somata clearly prevailed all along the rostrocaudal axis with a peak in L5 ganglion. While the number of small
bNOS-IR neurons clearly outnumbered NADPHd-stained and NADPHd-unstained somata in S1–S3 ganglia, an inverse relation appeared
comparing the total number of medium-sized NADPHd-stained and NADPHd-unstained somata compared with the number of moderate
and intense bNOS-IR neurons. Densitometry of bNOS-IR and NADPHd-stained neurons in lumbar and sacral ganglia revealed two
distinct subsets of densitometric profiles, one relating to more often found medium-sized bNOS immunolabelled and the other,
characteristic for moderately bNOS immunoreactive somata of the same cell size. Considerable differences in catalytic nitric
oxide synthase activity, determined by conversion of 3H]arginine to 3H]citrulline were obtained in lumbosacral dorsal root ganglia all along the lumbosacral intumescence, the lowest (0.898± 0.2
dpm/min/μg protein) being in the L4 dorsal root ganglion and the highest (4.194± 0.2 dpm/min/μg protein) in the S2 dorsal
root ganglion. |
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Keywords: | densitometry nitric oxide expression nitric oxide activity neuromodulator primary sensory neurons |
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