Changes of NADPH-diaphorase activity in the lumbosacral intermediolateral neurons of the rat after pelvic axotomy

Moderately different NADPH-diaphorase positivity in the selected peripheral nerves after ischemia/ reperfusion injury of the spinal cord in rabbit

1. To vicariously investigate the nitric oxide synthase (NOS) production after spinal cord injury, NADPH-d histochemistry was performed on the selected peripheral nerves of adult rabbits 7 days after ischemia. The effect of transient spinal cord ischemia (15 min) on possible degenerative changes in the motor and mixed peripheral nerves of Chinchilla rabbits was evaluated. 2. The NADPH-diaphorase histochemistry was used to determine NADPH-diaphorase activity after ischemia/reperfusion injury in radial nerve and mediane nerve isolated from the fore-limb and femoral nerve, saphenous nerve and sciatic nerve separated from the hind-limb of rabbits. The qualitative analysis of the optical density of NADPH-diaphorase in selected peripheral nerves demonstrated different frequency of staining intensity (attained by UTHSCSA Image Tool 2 analysis for each determined nerve). 3. On the seventh postsurgery day, the ischemic spinal cord injury resulted in an extensive increase of NADPH-d positivity in isolated nerves. The transient ischemia caused neurological disorders related to the neurological injury--a partial paraplegia. The sciatic, femoral, and saphenous nerves of paraplegic animals presented the noticeable increase of NADPH-d activity. The mean of NADPH-diaphorase intensity staining per unit area ranged from 134.87 (+/-32.81) pixels to 141.65 (+/-35.06) pixels (using a 256-unit gray scale where 0 denotes black, 256 denotes white) depending on the determined nerve as the consequence of spinal cord ischemia. The obtained data were compared to the mean values of staining intensity in the same nerves in the limbs of control animals (163.69 (+/-25.66) pixels/unit area in the femoral nerve, 173.00 (+/-32.93) pixels/unit area in saphenous nerve, 186.01 (+/-29.65) pixels/unit area in sciatic nerve). Based on the statistical analysis of the data (two-way unpaired Mann-Whitney test), a significant increase (p< or =0.05) of NADPH-d activity in femoral and saphenous nerve, and also in sciatic nerve (p< or =0.001) has been found. On the other hand, there was no significant difference between the histochemically stained nerves of fore-limbs after ischemia/reperfusion injury and the same histochemically stained nerves of fore-limbs in control animals. 4. The neurodegenerative changes of the hind-limbs, characterized by damage of their motor function exhibiting a partial paraplegia after 15 min spinal cord ischemia and subsequent 7 days of reperfusions resulted in the different sensitivity of peripheral nerves to transient ischemia. Finally, we suppose that activation of NOS indirectly demonstrable through the NADPH-d study may contribute to the explanation of neurodegenerative processes and the production of nitric oxide could be involved in the pathophysiology of spinal cord injury by transient ischemia.

Nitric oxide synthase neurons in the rodent spinal cord: distribution, relation to Substance P fibers, and effects of dorsal rhizotomy

The indirect immunofluorescent method was employed to investigate the distribution of neuronal nitric oxide synthase-like immunoreactivity(nNOS-LI) in the spinal cord of the golden hamster and to compare it to data obtained from rats. Immunoreactive neurons were found throughout the cervico-sacral extent in the dorsal horn (mainly in laminae I-III) and in the preganglionic autonomic regions, i.e., the sympathetic intermediolateral nucleus (IML), lateral funicle (LF), intercalated region (IC), the area surrounding the central canal (CA), and the sacral preganglionic parasympathetic cell group. While the distribution of immunoreactive cells was generally similar in both species, some differences were observed. For example in the hamster LF, a higher percentage of stained neurons was seen than in the IML, while the situation was rather inverse in the rat. In order to study the coincidence of nNOS-LI in the population of preganglionic sympathetic neurons (PSN) that innervate the superior cervical ganglion (SCG), these were identified by retrograde axonal transport of fluoro-gold (FG) following unilateral injection into the SCG. PSN were localized ipsilateral to the injection site mainly in the IML and LF of spinal segments C7-Th4. The portion of double-labeled neurons of the IML were lower in hamster (17% in C7, 34% in C8) of FG-labeled cells) than in rat (47% in C8, 77% in Th2), while in the LF of segments C8-Th2 in both species the majority of FG-neurons contained nNOS. While only very few double-labeled neurons were detected in the IC in hamster and rat, a striking difference was observed in the CA, where no double-labeled neurons were found in hamster, but up to 50% in rat. Double immunofluorescence detection of nNOS and substance P (SP) showed that in both the autonomic regions and the dorsal horn, SP-LI fibers and puncta were present in close spatial relationship to nNOS-LI cell bodies. These results were basically identical in the hamster and rat. Unilateral transection of the dorsal roots of segments C6-Th2 in rats resulted in a clear reduction of SP-LI structures in the dorsal horn 5 days after rhizotomy, but not in the autonomic regions. Compared to the unlesioned side, the numbers of nNOS-LI neurons in the superficial laminae of the dorsal horn were reduced to 32-46% in the lesioned segments, and to 53% and 87%, respectively, in the two segments cranial to the rhizotomized segments but remained unchanged caudally to the lesion. Numbers of nNOS-LI cell bodies in the autonomic regions were not altered following dorsal root transection. The present study provides data on the widespread distribution of nNOS in the spinal cord of golden hamster and describes the partial coincidence of the enzyme in PSN. The effects of dorsal rhizotomy on nNOS-LI neurons in the dorsal horn reveal that primary-afferent fibers provide a stimulatory influence on neurons of the dorsal horn to generate the gaseous neuroactive substance, nitric oxide.

Melatonin attenuates neuronal NADPH-d/NOS expression in the hypoglossal nucleus of adult rats following peripheral nerve injury

Oxidative stress and massive production of nitric oxide (NO) have been implicated in the neuropathogenesis following peripheral nerve injury. This study was aimed to ascertain whether melatonin would exert its neuroprotective effect on the lesioned hypoglossal neurons after peripheral axotomy, since it is known to reduce the oxidative damage in a variety of experimental neuropathologies in which NO is involved. Right-sided hypoglossal nerve transection was performed in adult rats following which the animals were given two different doses of melatonin administered intraperitoneally for 3, 7, 14, 21 and 30 successive days. Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and neuronal nitric oxide synthase (nNOS) immunohistochemistry were carried out to detect the neuronal NADPH-d/NOS expression in the hypoglossal nucleus (HN). At various time intervals following axotomy, the neurons in the affected HN were induced to express NADPH-d/NOS reactivity on the lesioned side peaking at 14 days. However, the enzyme expression was markedly depressed by melatonin treatment in a dose-dependent manner in terms of frequency of labelled neurons and staining intensity. It is suggested that the suppressive effect of melatonin on NADPH-d/NOS expression may be attributed to its antioxidant properties. Hence, in consideration of therapeutic strategies for reducing the oxidative stress following peripheral nerve injury, melatonin may prove to be beneficial.

The effect of electrolytic thalamic lesions on the NADPH-diaphorase activity of neurons of the laterodorsal tegmental and pedunculopontine nuclei in rats

Cholinergic neurons of the mesopontine complex have extensive ascending projections to the forebrain: the laterodorsal tegmental nucleus extensively innervates the anterior thalamus, the anteroventral nucleus in particular, whereas the pedunculopontine nucleus has widespread projections to both the thalamus and extrapyramidal structures. Most of their neurons express nitric oxide synthase (NOS) activity. Following electrolytic lesions of the anteroventral thalamic nucleus, nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd) activity in neurons of the laterodorsal tegmental nucleus changed drastically. The intensity of NADPH-diaphorase staining increased in laterodorsal tegmental neurons ipsilateral to the lesion side, but decreased contralaterally. The intensity of the NADPH-diaphorase staining of neurons of the pedunculopontine nucleus, however, remained unchanged bilaterally. After partial lesions of the anteroventral thalamic nucleus a similar effect was noted. In contrast, large electrolytic lesions involving other thalamic nuclei or extrapyramidal structures did not change the number of NADPH-diaphorase neurons or their intensity of staining in the laterodorsal tegmental nuclei. These data show that electrolytic lesions of target areas can lead to an upregulation of NOS expression in the parent cell bodies, provided that there is no wide collateralization as found for the pedunculopontine nucleus.

Axotomy increases NADPH-diaphorase activity in the dorsal root ganglia and lumbar spinal cord of the turtle Trachemys dorbigni

Seven days after transection of the sciatic nerve NADPH-diaphorase activity increased in the small and medium neurons of the dorsal root ganglia of the turtle. However, this increase was observed only in medium neurons for up to 90 days. At this time a bilateral increase of NADPH-diaphorase staining was observed in all areas and neuronal types of the dorsal horn, and in positive motoneurons in the lumbar spinal cord, ipsilateral to the lesion. A similar increase was also demonstrable in spinal glial and endothelial cells. These findings are discussed in relation to the role of nitric oxide in hyperalgesia and neuronal regeneration or degeneration.

In vitro motility disorders associated with displaced abomasum in dairy cows

The objective of this study was to investigate in vitro abomasal motility in dairy cows diagnosed with displaced abomasum. Longitudinal muscle myenteric plexus preparations originating from the abomasal antrum of control cows, and cows diagnosed with left displaced abomasum (LDA), right displaced abomasum (RDA) or abomasal volvulus (AV) were used. In control preparations electrical field stimulation evoked an immediate cholinergic contractile response exceeding amplitude of basal contractions by 60%. In contrast, contractile activity was significantly inhibited during electrical stimulation in LDA, RDA and AV by 47%, 66% and 45%, respectively. This inhibition was reversed in the presence of L-NAME. The staining intensity of NADPH-positive myenteric neurones was significantly higher in displaced abomasa than in controls. Concentration-response curves indicated that preparations from displaced abomasa showed reduced sensitivity to acetylcholine. This study demonstrated motility disorders in displaced abomasa in vitro. The results suggested that abomasal displacement is associated with malfunctions at the level of the intrinsic nervous system combined with impaired cholinergic muscle responses. There appeared to be a predominance of nitrergic inhibitory mechanisms over excitatory mechanisms. These results might be of significance for diseases associated with gastric hypomotility and emptying disorders.

Differential vulnerability of autonomic and somatic motor neurons to N-methyl-D-aspartate-induced excitotoxicity

Two closely-related subsets of spinal motor neurons are differentially vulnerable in the degenerative neurological disease amyotrophic lateral sclerosis. Autonomic motor neurons (i.e. preganglionic sympathetic neurons) survive in this disorder, whereas most spinal somatic motor neurons do not. The present study was undertaken in order to begin to understand the phenotypic differences between the two motor neuronal subsets which might contribute to this differential survival. Organotypic slice cultures of postnatal rat thoracic spinal cord were maintained in defined medium for one to 12 days in the presence or absence of N-methyl-D-aspartate or its antagonist, D-amino-phosphonopentanoic acid. Autonomic motor neurons that were stained for either nicotinamide adenine dinucleotide phosphate reduced diaphorase or choline acetyltransferase only were both able to tolerate 50 microM N-methyl-D-aspartate treatment for over seven days in culture with no apparent adverse effects. In contrast, cultures maintained for only one day in medium containing 50 microM N-methyl-D-aspartate showed a dramatic and highly significant decrease in the numbers of neurofilament-positive somatic motor neurons, as well as nicotinamide adenine dinucleotide phosphate reduced diaphorase-positive interneurons. These N-methyl-D-aspartate-induced effects were dose-dependent and blockable. The results of this investigation indicated that autonomic motor neurons and somatic motor neurons were differentially susceptible to N-methyl-D-aspartate-induced excitotoxicity, and that the resistance of autonomic motor neurons to this insult appeared to be independent of the nicotinamide adenine dinucleotide phosphate reduced diaphorase phenotype.