Spinal cord NADPH-diaphorase histochemical staining but not nitric oxide synthase immunoreactivity increases following carrageenan-produced hindpaw inflammation in the rat.
Recent reports suggest that NADPH-diaphorase (NADPH-d) may be a histochemical marker for neuronal nitric oxide synthase (nNOS) in the central nervous system. Carrageenan-produced unilateral hindpaw inflammation in the rat results in a bilateral increase in NADPH-d in spinal cord neurons. This suggests there would be a bilateral increase in NO, which mediates thermal hyperalgesia. However, carrageenan-produced unilateral hindpaw inflammation results in hyperalgesia of the inflamed hindpaw only. This study determined (1) if neurons that labeled for NADPH-d following carrageenan-produced unilateral hindpaw inflammation colocalized nNOS, and (2) whether there was an increase in nNOS-ir neurons following inflammation. Following unilateral hindpaw inflammation, double labeling of tissue sections and single labeling of alternate serial sections revealed a lack of colocalization or mismatch between NADPH-d histochemical activity and nNOS-like immunoreactivity in neurons in lamina I, the dorsolateral funiculus and lamina X. Quantitative analysis showed no difference in the number of nNOS-ir neurons and NADPH-d labeled neurons in the superficial laminae of the spinal cord in non-inflamed animals. Following unilateral hindpaw inflammation, there was a 34% increase in the number of NADPH-d labeled neurons but no increase in the number of nNOS-ir neurons. These results indicate that nNOS-immunoreactive neurons and NADPH-diaphorase stained neurons are not identical and that nNOS does not increase as a result of hindpaw inflammation, leaving the source of NO involved in thermal hyperalgesia following injury in question.
Traub
R J
RJ
Department of Pharmacology, University of Iowa College of Medicine, Iowa City 52242, USA.
Solodkin
A
A
Meller
S T
ST
Gebhart
G F
GF
D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000818:Animals; D002351:Carrageenan; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism; D007150:Immunohistochemistry; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D019001:Nitric Oxide Synthase; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism*
D002351:Carrageenan; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D009252:NADPH Dehydrogenase