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The aim of the present study was to examine changes in the level of neuronal nitric oxide synthase (nNOS) and parvalbumin (PV) in dorsal horn of the rat lumbar spinal cord segments (L2–L6) 7 and 14 days after thoracic spinal cord transection. Our data show that staining of control transverse spinal cord sections with nNOS antibody provided an intense labeling of small round or bipolar nNOS- immunoreactive (IR) cells bodies, fi bers and terminal like structures which were distributed throughout lamina II and formed a dense IR band. The large multipolar nNOS-IR cells with stellate or elongated cell bodies were occasionally seen in the deeper layers (laminae III–IV). A decreased density of fi berlike and the loss of somatic nNOS staining was found in dorsal horn layers after transection at both time points. A quantitative assessment of nNOS IR disclosed a strong decrease in the number of small neurons in superfi cial laminae (laminae I–III). In addition, an intense PV-IR band, consisting of terminal like structures in lamina II under normal conditions, was signifi cantly reduced due to spinal cord transection. The present study indicates a considerable decrease in the number of nNOS-IR neurons in superfi cial dorsal horn, where NO modulates the activity of inhibitory GABA-ergic interneurons. The changes in expression of both the calcium binding proteins in dorsal horn may modulate nociceptive transmission. Support: APVV grant 0314-06 and VEGA Grant 2/0015/08 from the SAS.
Nitric oxide, a diffusible molecule which is constitutively expressed by neuronal isoform of nitric oxide synthase (nNOS) acts as an important non-conventional neurotransmitter in the nervous system. The distribution of nNOS-immunoreactive (-IR) and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) positive neurons was studied by immunohistochemical and histochemical methods in upper lumbar (L1- L3) and lower lumbar and sacral (L4-S4) dorsal root ganglia (DRGs) and in relevant spinal cord segments after 15 min ischemia followed by 7 and 14 days of reperfusion. The intensity of nNOS-IR and NADPHd positivity was evaluated by densitometric analysis, using a software UTHSCSA Image Tool. A quantitative immunohistochemical and histochemical study have shown a strong vulnerability of nitrergic neurons in the spinal cord to transient ischemia and the following reperfusion periods. In addition, our results clearly show the increase of nNOS-IR/ NADPHd positivity in spinal ganglia laid outside the spinal cord. Distribution character of nNOS-IR/NADPHd positive fi bers coming out from DRGs refl ects the increase of nNOS-IR and NADPHd positivity in thin and thick myelinized axons of dorsal roots and dorsal funiculi. These results explain the participation of nitrergic system in nociceptive and proprioceptive circuits in the spinal cord. Supported by the APVV 0314 -06 and VEGA grants 2/0110/08 and 2/0015/08.
The NO-sensitive guanylyl cyclase (sGC) as a major type of cyclic guanosine monophosphate (cGMP) - forming enzymes represents the best characterized receptor for the signal molecule nitric oxide (NO) produced by the NO synthases. Relatively high levels of the sGC are found in lung, brain and platelets, but little is known about the NO-cGMP signalling in the spinal cord. Our study was focused on NO-sGC signalization in bulbospinal respiratory pathway. We used a model of spinal cord hemisection performed at C2-C3 segmental level. After spinal cord injury the animals (adult rats) survived for eight days. The expression of neuronal nitric oxide synthase (nNOS) and β1 subunit of sGC was identified by immunohistochemical fluorescent method in ventral respiratory group (VRG) of medulla and in phrenic nucleus (PN) located at C4-C5 segmental level. In addition, the retrograde tracer Fluorogold (FG) was used to label neurons of VRG. These neurons were nNOS-immunoreactive. Two days after FG injection into the phrenic nucleus (PN), we revealed many FG fluorescent neurons mostly contralaterally to the site of injection. In control group, we noted nNOSfluorescent terminals of VRG neurons around beta 1 soluble guanylyl cyclase (ß1sGC) fluorescent motoneurons in PN. Spinal cord hemisection caused a significant decrease of the nNOS- and Synaptophysin (SYN) fluorescent terminals around alfa motoneurons in contralateral PN 8 days after hemisection. On the side of injury, nNOS/SYN fluorescent puncta were detected around phrenic motoneurons only sporadically. Phrenic alfa motoneurons responded to C2-C3 hemisection by a loss of ß1sGC positivity. These results together suggest that bulbospinal respiratory pathway is acting through NO-sGC. The experimental work was supported by VEGA Grant 2/0015/08.
In this review we briefly discuss animal experiments involving acute traumatic spinal cord injury (SCI) and the need for larger animals in testing experimental therapies. This literature overview, including the discussion of our own results from animal models, examines the use of hypothermia as a treatment method for SCI. Finally, we report the results of hypothermia application in clinical trials. Minipigs have been proposed as a potentially preferable model to rodents (typically rats) for predicting outcomes in human SCI due to their closer anatomical similarity to humans. In various animal studies, hypothermic treatment applied in the acute phase after SCI has resulted in neuroprotective effects, most likely due to inhibition of blood flow and oxygen consumption and reduction of overall metabolic activity and inflammation, resulting in improved nerve tissue sparing. Small‑scale human clinical trials have been carried out, involving general (whole‑body, systemic) or local hypothermia (close to the SCI site), with encouraging results. Nevertheless, further multi‑center, randomized, double‑blind studies with much larger patient numbers are necessary so that protocols can be standardized in order for hypothermia treatment to be reliably applied in clinical practice.
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